By Karen Erens
How many night dives have you done?
Are you still getting excited about diving in the dark, or are you getting a bit bored?
Have you ever seen bioluminescence during one of your night dives? You will only see this when you turn off your dive light (and all other dive buddies around you should also do this) and move your hands in the dark water in front of you. When your eyes are used to the dark, you’ll see some small particles lighting up. This is called bioluminescence produced by plankton. It is light emitted by living organisms, like fireflies, but it is produced by plankton in the sea.
Just a few months ago, I learned an even more exciting way of night diving!
Does the name “ostracod” ring a bell? No? Let me explain the phenomenon.
Ostracods are a class of very small crustaceans, also known as “seed shrimps.” As the name suggests, Ostracods are very small. They are usually part of the zooplankton and are only about one millimetre in size, which means you will not see them while diving. However, Ostracods inhabit almost all aquatic environments.
So why do I write about them if we divers will not see them underwater? Why are they so special?
It is their bioluminescence which makes them very interesting for divers. In short, they glow in the dark to distract predators or signal an alarm to other Ostracods. Usually, they glow when they are disturbed or touched by spewing out glowing mucus. You can see it all for yourself; just try moving your arm in the water on a dark night dive, and you’ll see small glowing particles in the water. And that’s exactly what makes them so interesting for divers.
Once a month, they reproduce and need to attract the attention of other Ostracods while using their ability to glow. It is not the normal glowing they show while getting disturbed; this kind of glowing is of a different kind. They give the best of themselves as they have to attract male or female Ostracods.
As they start glowing on that specific night, you’ll see dots of bright light climbing up in the water or going down in a straight line. Once the activity of the Ostracods picks up, as a diver, you are surrounded by all these dotted glowing lines in the water. It gives a very special and unique feeling to be part of this nice underwater spectacle.
Let me explain how to organize this kind of night dive in order to see them. It is only accessible for divers with a night dive specialty certification (or at least some night dive experience), and you have to consider some of the rules of nature.
Maybe it is also a good idea to try it a few times yourself (with another colleague) before organizing such a dive for your customers. This way, you will be able to fine-tune this special night diving experience.
Listed below are some points for you to build into your plan.
- The Caribbean is home to this kind of ostracod glowing with a “blueish” light
- Make sure that you know the date of the next full moon
- The Ostracods are active between 3 and 5 days after a full moon, but the best result is on day 4 or 5 after a full moon.
- Find an easy dive spot to enter the water, not too deep and preferably with soft corals and no light pollution.
- It is important to be in the water 35-40 minutes after sunset, so you can still use the last daylight to set up the gear and go in the water.
- Do not use any dive lights when you enter the water. Also, do not use lights while spotting the Ostracods. You will lose your night vision, and the Ostracods will disappear. On the other hand, it might be rather challenging to do a night dive without light, so make sure you and your buddies are trained in night diving and choose a dive spot you know well, like the back of your hand.
- Be patient; just let your eyes get used to the twilight
- The Ostracod show will start 45 minutes after sunset. It begins slowly with just some tiny glowing dots on the reef, but soon after, you’ll see that the glowing is getting stronger and forming dotted glowing lines going up or down.
- Make sure you stay close to your buddy to avoid losing each other on the dive. Night diving without a dive light might be challenging. But it is a different and exciting way of diving! I like it very much, you see so much more than you would expect, and if you pay attention to your buddy, it is easy NOT to lose them.
- If you’ve enjoyed enough ostracod activity, switch on your lights and continue with a normal night dive. Be aware of your air supply as time passes very fast in this way, doing a “double” night dive!
At this moment, the ostracod night dives are mainly organized in Bonaire. I don’t know why this is, but I would say that many night dives are done there as the dive sites are easily accessible.
I also did an Ostracod dive in Curaçao as I was there at the perfect time of the month. And guess what? After a slow start and being patient, I was surrounded by Ostracods, although they started a bit later than 45 minutes after sunset. So I guess there are more good dive sites for spotting this magical phenomenon. So why not try it?
So what stops you from searching for a good night dive spot? Check when is the next full moon, wait the days and go night diving without light.
Let’s see if there are more good ostracod dive spots around the Caribbean? Maybe you’re surprised, and you’ll encounter this impressive phenomenon.
During the following months, I will visit the Dominican Republic, the British Virgin Islands and Turks & Caicos, and I have already planned my ostracod night dives on these spots.
Where will you be diving during the following months?
Share your findings with all of us, be part of our Ostracod research and join the ScubaBiz Facebook group to share and learn more about this recently discovered phenomenon!
We will be waiting for your information!
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