Bioluminescence is the production and emission of light by a living organism. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria and terrestrial arthropod such as fireflies.
There are five bioluminescent bays in the world: Luminous Lagoon in Jamaica, Halong Bay in Vietnam, and Puerto Rico’s Laguna Grande, La Parguera, and Mosquito Bay.
Are you tempted to expand your scuba knowledge, but don’t know where to start? Take our fun quiz to get some inspiration…
Q1: What do you love most about diving?
A: Breathing underwater
B: Meeting new friends
C: Visiting a whole new world
D: Trying out all the scuba gear
E: Nailing neutral buoyancy
Q2: You’re diving a shipwreck… what are you thinking?
A: I can’t wait to explore below deck!
B: Can we remove some of that fishing net?
C: I wonder what this looked like before sinking?
D: Boilers… propellor… cannons… awesome!
E: Time to practice my wreck diving skills
Q3: You’re planning your next trip. What’s your preference?
A: Anything, as long as it’s new and exciting
B: Encounters with underwater creatures
C: Somewhere with impressive scenery
D: Making sure there’s WiFi and somewhere to charge batteries
E: Educational trips with the chance to learn something new
Q4: What’s your favourite après-dive activity?
A: Booking the next adventure!
B: Sharing stories with my dive buddies
C: Taking in the local sights and cultures back on land
D: Downloading my dive profiles onto my computer
E: Reflecting on my dive experience
Underwater cities offer divers the chance to immerse themselves in history. Discover ancient cultures, explore an underwater prison, or follow in the steps of archeologists by visiting some of these underwater cities.
Canada – Lost Villages of the St. Lawrence River The St. Lawrence River is home to nearly a dozen “Lost Villages.” The historic towns (some were founded back in the late 1700’s) were sacrificed to the St. Lawrence Seaway and Power Project. Highways and railways were rerouted, residents relocated, and in July 1958, the villages were flooded. View aerial photos of the submerged towns.
China – The Lion City in Qiandao LakeOne hundred feet (30 meters) beneath Qiandao Lake in China lies Lion City, also known as Shi Cheng. Intentionally flooded in 1959 as part of a hydroelectric dam project for the nearby city of Hangzhou, Lion City was built during the Han Dynasty approximately 1,000 years ago.
Underwater features include lions, dragons, and phoenixes carved in stone alongside pagodas and temples from the Ming and Qing Dynasties. This dive is recommended for advanced divers with experience diving in low-visibility conditions. An overzealous kick can disturb the fine silt at the lake bottom and visibility can quickly drop to zero. Read more about diving The Lion City.
Rummu, Estonia – Underwater Prison At the bottom of Rummu Lake is a former Soviet prison. With the right permission and a proper dive guide, it’s possible to safely explore the underwater buildings and sunken forest. The maximum depth is about 42 ft/13 m, with average visibility around 15ft/5 meters.
Greece – Pavlopetri Pavlopetri is the modern name given to a Bronze Age city located off the coast of Laconia. Researchers believe it may have been part of the Minoan dynasty and an earthquake caused the city to sink beneath the waves. Pavlopetri is a UNESCO site and not open for recreational diving. But you can snorkel above the 5,000 year old city and explore land-based ruins nearby.
Israel – Ruins of Caesarea and Underwater Museum Divers and snorkelers can participate in an archeological adventure at the Caesarea Underwater Archaeological Park. Explore the underwater ruins of docks, warehouses, boardwalks and ancient shipwrecks.
Visitors receive a guide where each number on a map corresponds to a point of interest underwater. Divers can follow a rope from one point of interest to the next and learn about the ancient city.
Italy – Sunken City of Baiae In its heydey, Baiae was a hotspot for wealthy and powerful Romans. Today, it’s a great place for divers and snorkelers to dive among ancient statues relics and beautiful mosaics dating from the first century BCE.
Norway- Lake Lygnstøylsvatnet In 1908, a small Norwegian village unexpectedly became a future scuba diving destination when a rockslide dammed the nearby River Lygna. As water levels rose, the village was evacuated. Today, divers can float across the submerged bridge into the sunken village. Read more about diving Norway’s underwater town.
A dive computer gives you all the important information you need to dive safely, in real-time. Without one, you’re stuck working with a dive watch, dive tables, and a depth gauge to figure out vital calculations like decompression time, safe diving time, etc.
A dive computer does everything depth gauges and dive tables do in one convenient package, and lets you spend more of your dive having fun rather than racking your brain and trying to do mental math or guess about your safety!
Can you dive without one? Sure. Do you really want to? I don’t think so! Computers allow you to be much more flexible, spontaneous, and just plain safe under the waves.
Here’s how to find your perfect dive computer:
Decide on your budget
Dive computers can cost anywhere from $150 to $1,500+ USD.
Recreational divers probably don’t need to spend more than $500 USD, if that. You can get some really great models for less, and you’ll only need to pay more if you want a technical computer that features air integration.
Typically, serious divers and more experienced folks who want air integration would want to purchase the top-of-the-line computers. An exception might be if you’re a committed newcomer with an ample budget, who wants to start right out with air integration.
More expensive computers have more versatility with gas mixes, algorithms, and navigation settings. The more you spend, the more customizable your computer will be overall. You’ll also pay a premium for air system integration.
Consider air system integration
Some computers are “independent,” which means that they work on their own. They’ll replace a few pieces of your dive equipment (depth gauge, compass, etc.), but they won’t actually connect to your air system. For the majority of recreational divers, they’re all you really need.
Most technical (and more expensive) dive computers are “integrated,” which means that they connect to your regulator and air supply. A computer with air system integration can actually track the air in your tank, and give you dead-on calculations. Most recreational models don’t have air system integration, which keep costs down for your computer and for the rest of your gear.
Your computer figures out dive times and no decompression schedules by plugging in data like depth, time, and pressure into an algorithm. Some even have multiple algorithms on the same model! There are lots of different algorithms used, and they each have a bias. They’re all more or less conservative, meaning they’ll take either more and longer stops or fewer and shorter stops. The same is true of their no-fly recommendations and total dive time allowances. When you’re comparing dive computer options, be sure to get a sense of the relative conservatism of each model.
The less experienced you are, the more conservative a computer you want. You never want to take any chances when you’re starting out. Even experienced divers like me often use more conservative algorithms to stay safe.
Your own body is as important a consideration as your experience level. If you’re more susceptible to decompression sickness, you’ll want to stick with conservative algorithms, regardless of experience.
The best dive computers give you a few different algorithm options.
Backlight: I would never buy anything without a backlight. You might not think you need one, but a backlight is one of those things you really want to have if something goes wrong.
Water-activation: Water-activated dive computers turn on and start calculating as soon as they hit the surface. Since all of us forget to turn things on sometimes, this is one convenience you don’t want to do without. It’s better to pay a bit more and be able to trust your computer to work even when you forget to tell it to!
Alarms: alarms are the feature that guarantee you’ll see urgent alerts when you need to, because even the most attentive diver occasionally forgets to look at their computer. Look for alarms that are adjustable and easy to program. You want to be able to use whatever is going to catch your attention, whether it’s noise or flashing lights.
Basic display features: any good dive computer should show you the basics at a glance. Those are: maximum depth, current depth, dive time, and no-fly/no-stop time.
Choosing between models
Think about where you are now with your experience level and dive habits. What kind of dives are you doing now? Where do you want to be a year from now? Will you be happy with something basic, or do you want lots of room to grow?
Knowing your own preferences is the most surefire way to insure you’ll be happy with the computer you buy. So, try as many as you can while you’re at the rental stage. Go to shops and play around with demo models.
Make sure it’s a good fit for you:
Can you see everything you need to? Does it fit well with your wrist/equipment?
What about the display? Is it set up in a way that makes sense to you? Do you find it easy enough to navigate?
*Do you like to take an extra deep stop? This practice has been shown to have noticeable benefits over the traditional safety stop pattern, so look for deep stop features on newer dive computers. If you want to get super technical, this study breaks down all the reasons to take deep stops in detail.
Article written by Josh Kaplan
Josh Kaplan is a passionate scuba diver, shipwreck explorer, and world traveller. He’s always exploring new destinations around the world and writing about them for various publications. He also reviews dive gear and writes buying guides for scubalist.pro, a site which aims to connect divers with affordable, high-quality equipment.
Many wrecks — like Scapa Flow’s battleships — bear the scars from exciting or tragic histories, and divers flock to get a first-hand glimpse. Some wrecks hold cultural importance, attracting archaeological research and protection, while others may have been purposefully sunk to provide a new home for the ocean’s flora and fauna.
Whatever the significance, we each hold a responsibility to make sure there’s something left for future generations to explore. While natural deterioration will inevitably take over, here are five tips on helping to preserve our favourite wrecks for as long as possible.
Take photos, not souvenirs
Never remove things from a wreck. Yes, that porthole might look great above your fireplace, but it looks even better in its original home — and by leaving it alone, other divers can appreciate it time and time again. If you do stumble across something unusual — like treasure or unexploded munitions — take a photo, note its location, and report it to your dive operator or the local marine authorities.
Nail neutral buoyancy
Thanks to time, rust, and corrosion, wrecks can be unstable structures that might collapse under your weight if you grab, pull, or land on them. That’s bad news for you and for the wreck, and a good motivation to keep your buoyancy under control. Think about taking the PADI Peak Performance Buoyancy Specialty course to perfect this crucial skill.
Don’t tie things to the wreck
Tying a dive boat’s mooring lines to a wreck is a sure-fire way to rip sections of it apart in no time; the Thistlegorm is a famous example of the damage this causes. If you notice crew doing this, ask them to consider alternative anchorage, and choose dive operators that follow the 10 Tips to Protect the Ocean Planet. Avoid tying your own reel and lines to a wreck — for the same reason, just on a smaller scale.
Focus on the outside
Diver’s bubbles trapped inside metal structures can speed up the process of oxidisation and decay. So, before venturing inside, consider if you really need to; often the exterior is just as fascinating.
Are you keen to enhance your exploration in wreck diving?
If you’ve not yet discovered the mystery and magic of a wreck dive, you’re missing out! The PADI Wreck Diver Specialty course is popular because it offers rewarding adventures while observing responsible wreck diving practices.
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