Spider Crab Pyramid

No stranger to capturing unique and wonderful scuba diving experiences in Melbourne, Australia, PADI scuba diver PT Hirschfield has recently come across a pyramid consisting of hundreds of spider crabs.

In 2014, PT witnessed thousands of spider crabs migrating in Port Philip Bay and this recent encounter again highlights the interesting behaviour of these marine critters.

There are numerous theories about the spider crab migration, however the most common thought is that the crabs converge in this particular area to moult their exoskeleton and mate.

10 Facts About Seagrass You Probably Didn’t Know

Emma Daffurn

1. There are around 50 different species spread all over the globe

Seagrasses evolved roughly 100 million years ago from grass on land, which is why vast marine meadows can be reminiscent of our terrestrial grasslands. Often confused with seaweed (which is a relatively simple algae), seagrasses are organized into four distinct plant families PosidoniaceaeZosteraceaeHydrocharitaceae, and Cymodoceaceae.

2. They LOVE the sunshine

Seagrasses are found all over the world, in every continent except Antarctica. However, they require lots and lots of sunlight to photosynthesise, so the depths at which they occur in the ocean are limited by light availability.

If you currently find yourself near to a bay, lagoon or estuary, we’re willing to bet you’re near some seagrass too.

3. They’re ‘ecosystem engineers’, literally creating the foundations of life

Not only do seagrass meadows pump out a staggering amount of oxygen each day (~100,000 litres per hectare!), they also bring stability to the ocean floor with their extensive root systems.

This means that seagrasses literally alter the ecosystem around them for the better, creating a welcoming habitat for marine creatures great and small. 

4. They can absorb carbon up to 35x faster than Amazonian rainforest

Yes, you read that right, 35x more effective! Seagrass meadows account for more than 10% of the ocean’s global carbon storage, whilst only covering around 0.1% of the ocean floor.

That adds up to roughly 27.4 million tons of CO2 annually.

Compare this with the 37.1 billion tonnes of CO2 produced by humanity in 2018 alone, and it soon becomes crystal clear that we need faster and stronger action to address accelerating climate change, like, yesterday.

Seagrass is just one promising method of doing so, and one that is undoubtedly close to divers’ hearts.

5. A single acre alone can support over a million species 

Why so close to divers’ hearts? Because of the awe-inspiring, quirky and beautiful marine creatures these habitats represent.

Let’s play a quick game: which of the species below does not rely on seagrass?

Thorny Seahorse

And the answer is…… you guessed it – none of them!

Every single one of these species – and more – rely on the habitats created by seagrass in one way or another.

The sad truth is that when the future of seagrass is uncertain, the future of these beloved marine creatures also comes under threat.

6. You can thank them for that 30m/98ft visibility

As seawater gets trapped in vast seagrasses, sediment and particles suspended in the water column become trapped too. This means cleaner, filtered oceans – the natural way.

When the seabed lacks seagrass, sediments are more frequently stirred up by winds which decreases visibility, and there is nothing to stop land-based industrial discharge or storm water runoff from washing right onto delicate coral reef systems.

7. They provide crucial refuge for numerous species of juvenile reef fish

Seagrass meadows are often referred to as nursery habitats, as their dense gardens trap and slow the flow of seawater, creating shelter for juvenile fish.

Juvenile Cuttlefish

Without seagrasses or mangroves to hide out in, these little ones become extremely vulnerable to predators in the open ocean or on the reef.

As with all life on earth, the ability to safely raise the next generation is critical to species survival. When this comes into question, so does the future of all life in the ocean.

8. They’re the true underdog when it comes to coastal community resilience

You’d be forgiven for thinking that the benefits of seagrass are limited to the ocean alone, but you’d be wrong!

The stabilizing effect of seagrass actually reduces flooding from storm surges and hurricanes by dissipating wave energy.

In a time of unpredictable, extreme weather events, this means safer, dryer and more resilient communities. The very same communities where you or your family live, work or spend vacation.

The good news? For every $1 invested in coastal restoration projects and restoration jobs, $15 in net economic benefit is created.

9. They’re under serious threat – disappearing at a rate of two football fields an hour!

Seagrass meadows are disappearing at an alarming rate, and we’ve already lost an estimated 29% globally in the last century. Why?

Natural Threats

  • Heavy storms, floods and droughts that make water conditions unfavourable (unfortunately, now being exacerbated by human-induced climate change)
  • Disruption by feeding predators as they search for food, including sea turtles and manatees

Human Threats

  • Removal by resorts who believe their guests prefer a white sandy seabed than a green meadow
  • Irresponsible boating practices including poorly thrown anchors and sailing in too shallow water
  • Agricultural and industrial run-off overwhelming the seagrass’s filtration abilities
  • Destructive fishing practices such as dredging (scraping the seabed, catching everything, then dumping by-catch overboard)
  • Blocking out of light in busy harbours and docks

With three species of seagrass on the endangered list, and a further 14% facing an elevated risk of extinction, now is the time to act.

10. We are the solution

As much as we have unknowingly collaborated across the planet to destroy seagrass habitats, we have the power to work together in protecting them.

As a global network of torchbearers, together we can save the ocean. There is still hope and there is still time.

Volunteers planting seagrass with The Ocean Foundation

Cold Water Photography Subjects

 Matt Testoni

Cold water can often be a deterrent to scuba divers. Indeed, chilling winter oceans have their additional challenges – however if you’re into underwater photography, it can definitely pay to face the cold conditions. The biodiversity in cold locations can often be greater than warm water dive sites, with the animals being larger and less commonly  photographed. Below are a few tips on why it’s worth bracing those icy conditions and what you might see.

Cold Water Photography - Leafy Sea DragonAll photos by Matt Testoni

Leafy Seadragons

Seadragons are a larger and more beautifully intricate relative of the seahorse. They occur only in Australia, from Sydney to Perth along the south coast. The Weedy Seadragon is the most commonly spotted of the group however if you can brave the 10 degree water of Rapid Bay in South Australia you may just be lucky enough to see a Leafy Seadragon. With multiple amazingly detailed and fascinating appendages, they awe every diver who encounters them. At over 30cm in size, they drift elegantly through the shallow waters using their camouflage to hide and hunt. They’re definitely at the top of the list for underwater photographers worldwide (and if they’re not they should be!)

Cold Water Photography - Fur Seals
Fur Seals

These amazing and curious animals are usually found in chillier areas, hanging around and sun baking on rocky shelves next the ocean. Fur Seals are not only an underwater photographer dream subject, they’re a must see and experience for all divers. The way the come say hello and play a few games with you is a truly unique underwater adventure. With amazing feats of acrobatics they dart around before stopping for a good stare right into your face – the perfect time for a photo or two. Don’t worry though! At no point will you feel threatened.

Cold Water Photography - Butterfly Perch
Schooling Butterfly Perch

In the southern oceans of Australia and New Zealand, thousands upon thousands of vibrant pink Butterfly Perch form dense schools that sit close to the ocean floor forming curtain like walls. Swimming through them makes you feel like a stage show actor, jumping through an opening night curtain. Load up your wide angle lens and get down past the 30 metre mark to see these beauties. Often they can be found in large numbers around shipwrecks adding great variety to what are already great dives and making for some truly unique photos.

Cold Water Photography - Giant Cuttlefish
Giant Cuttlefish

When most divers think of cuttlefish, they imagine small squid-like animals that pulsate with colour and are no bigger than your scuba mask. Visit the cold waters of Australia’s southern regions with this picture in mind and you will get a mighty shock! Here, Giant Cuttlefish are more than happy to come and say hello. Weighing in at over 10kg and reaching over half a metre, they float around with their massive arms, hunting fish and decorating their bodies with colourful displays. An encounter with these behemoths is definitely one for the photography bucket list! When you snap away at these animals, be sure to line the sun up in the background to capture those amazing underwater sun rays – cuttlefish will often pose for you in the perfect location, especially if you are calm and get to know them.

Cold Water Photography - spider crab migration
Spider Crab Migrations

Perhaps one of the most amazing cold water sites that no photographer should miss is the winter migration of Spider Crabs. These football sized crustaceans march into the shallows each winter forming a dense sea floor covering. At the right time there can be tens of thousands of individuals at any one dive site! Indeed you can almost swim in excess of 100m and barely see the ocean floor due to the layer of huge crabs that are slowly plodding along. Whilst the timing the migration right can be difficult, the reward is worth it. Make sure to stretch those strobe arms out wide however as the crabs will always fill your photographic frame!

Five Frogfish Facts

Megan Denny11 March, 2014

Frogfish are masters of disguise. Spot one during a dive and you will win the admiration of every diver in your group – especially photographers. Frogfish, a type of anglerfish, have a textured exterior that aids in their camouflage. While they do not have scales, their amazing ability to camouflage themselves serves as protection from predators. Frogfish vary in color and often have unique spines or bumps that change with their surroundings.

Here are some more interesting frogfish facts:

1. Unlike many animals that use camouflage as a defense from predators, frogfish mostly use their abilities to attract prey.
2. Frogfish have a modified dorsal fin that has a retractable lure resembling a shrimp, which is used to attract their prey. If their lure is eaten or damaged it can be regenerated.
3. Frogfish are carnivores. They eat fish, crustaceans and even other frogfish.
4. A frogfish’s mouth can expand to 12 times its resting size. This allows it to catch all sorts of prey.
5. Because frogfish lack a swim bladder, they use their modified pectoral fins to walk, or even gallop, across the seafloor (check out this great video of a frogfish in action).FrogFish yawningBy Steve Childs (Flickr: Painted FrogFish yawning)

There are many fish in the sea that use camouflage, but the frogfish is a real treat to see. Frogfish can be found in tropical and subtropical oceans and seas off the coasts of Africa, Asia, Australia and North America. Next time you take a dive in one of these regions take a closer look at the reef.

Have any frogfish spotting tips? Let us know.

You’ve Been Stung by a Jellyfish – Now What?

Cathy Evans20 October, 2017

Jellyfish Canada

Picture it. You’re on a dive taking in the beautiful marine life all around you when you feel something brush past your ankle. Immediately, an intense burning sensation travels up your leg, and you realize you’ve been stung by a jellyfish. Now what?

It depends on what kind of jellyfish stings you

There are over 2000 different types of jellyfish with some as large as adult humans and others smaller than a grain of salt.  Found in every ocean, lakes, and even in some freshwater bodies of water, roughly 70 of the 2000 species can hurt humans.Moon JellyfishMoon Jellyfish

Not So Bad

Moon jellyfish, otherwise called “saucer jellies,” “moon jellies,” or “common sea jellies,” are one of the most common types of jellyfish. Their moonlike bell shape and short tentacles make them easy to spot. They can be found in the Atlantic, Pacific, and Indian Oceans, mostly near the coast in warmer waters.

Though mostly benign, these jellyfish sometimes sting. However, the sting is mild in nature and restricted to a precise area of contact.


The lion’s mane jellyfish, otherwise known as the “hair jelly,” is one of the largest known jellyfish growing up to 120 feet/37 meters long. This species prefers the cooler waters of the Arctic, Northern Atlantic, and Pacific Oceans but can also be found in the southwestern Baltic all the way to Australia and New Zealand.

Due to the insane amount of tentacles (up to 1200), these guys can be dangerous both in and out of the water. It is reported that up to 50 people sustained jellyfish stings from a lion’s mane that washed ashore on a US beach. Like most other jellyfish, their tentacles can still fire even after they have died.

The stings are painful, causing localized swelling and redness, but are rarely fatal.Box JellyfishBox Jellyfish

Seek Help Immediately

The box jellyfish, otherwise known as the “marine stinger” or “sea wasp,” packs quite a punch, containing enough venom to kill 60 people. It is said that the box jellyfish is the deadliest creature in the ocean. “These dangerous jellyfish are common in the tropical Indo-Pacific, but some species of box jellies inhabit subtropical oceans, including the Atlantic and East Pacific. Species occur as far north as California, the Mediterranean and Japan and as far south as South Africa and New Zealand.”

That being said, if your dive ends with you encountering one of these, it does not mean your meeting will be fatal, but you should seek medical attention immediately.


The best course of treatment for all jellyfish stings is to rinse affected area with vinegar (avoid using freshwater), remove all visible tentacles, immerse the affected area in hot water, or use the localized application of a cold pack to alleviate pain. Look for signs of an allergic reaction and seek medical attention if necessary.

Treating jellyfish stings is just one of the many skills taught in the PADI Emergency Responder Course. Click here to learn more about EFR.


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