A new kind of night diving

How many night dives have you already 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’ll only see this when you turn off your dive light (and all other dive buddies around you should do this as well) 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 in the sea it is produced by plankton.

Just a few months ago, I have 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”, so as the name suggests ostracods are very small. They are usually part of the zooplankton and only about 1 mm in size, which means you will not see them while diving although the 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, shortly said, they glow in the dark in order to distract predators or to signal 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 of glowing. 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’re 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.

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. In this way you will be able to fine tune this kind of special night diving.

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 (or at least some night dive experience) and you have to take some of nature rules into consideration.

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 full moon, but the best result is on day 4 or 5 after 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.
Don’t use any dive lights if you enter the water. Don’t use lights while spotting the ostracods, you’ll blind yourself and they will disappear. 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 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 starts slowly with just some small glowing dots on the reef but soon after that you’ll see that the glowing is getting stronger and forming the dotted glowing lines going up or going down.

Make sure you stay close to your buddy in order not to lose each other on the dive. Night diving without a dive light might be challenging, it is a different and exciting way of diving! Personally 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 loose 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, I would say that many night dives are done there as the dive sites are easy accessible.

I also did an ostracod dive in Curaçao as I was there on the perfect time of the month and so why not try it. 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’s more good dive sites for spotting this magical phenomenon.

So what stops you from searching a good night dive spot, check when is the next full moon, wait 4 days and go night diving without light?

Let’s see if there’s more good ostracod dive spots around the Caribbean? Maybe you’re surprised and you’ll encounter this impressive phenomenon.

Where will you be diving during the next months?

Share your findings with all us, be part of our Ostracod research. We will be waiting for your information!