Subject: Let’s take a closer look at the external body parts of the Variable Thorny Oyster (Spondylus varians). Divers seldom get a good look at the beautiful undulated orange mantle of this bivalve due to the fact that when this creature detects light fluctuations or motion it closes its shells rapidly. The detection of light and movement is done by a row of primitive eyes (or eye-spots) situated between the mantle and the shell.
Technique: Turn on your lights from a short distance away (3m/10ft) and then approach the oyster very, very slowly without making sudden movements... Once close enough you can start filming, using your zoom if necessary. If you are unlucky and the oyster closes before you had a chance to film it then just move away because as long as your lights are on it, it won’t open soon. You might have to try a few times before you succeed.