“Why do we dive at night?” asked Jess in her briefing. The answer is varied but we all agreed that although seeing her dress up in neon T-shirt, fish-net tights and baseball cap is a highlight, seeing cool stuff underwater is the main reason.
One thing Jess wants to talk about (and the reason she’s wearing this amazing outfit) is bio-luminescence – sometimes confused with phosphorescence but there’s a big difference. Phosphorescence absorbs light and then beams it back out – it’s the stuff they put in dive computers, pressure gauges and compasses that means you can read them easily on a night dive and hopefully not get lost (more about getting lost later).
Bio-luminescence on the other hand is something actually produced by a living organism and then shines out as light. We see it in lots of marine animals and in some land animals too like in fireflies. It’s a clever chemical reaction involving a light-emitting pigment, an enzyme and some other proteins. OK let’s not fall asleep before the dive due to a science overload. Basically, marine plankton emits a tiny light when agitated so if we cover our lights and wave our arms quickly from side to side we can see a cool, underwater fireworks display. Jess is quick to remind us that the movement is side ways, not up and down. Up and down could have some undesirable effects on buoyancy!
So, what else is there to see at night? Jess tells us all about hunting moray eels, mating octopus, the glowing eyes of thousands of shrimp. There will be feather stars “walking” around, puffer fish sleeping on top of table corals and much more. It sound’s amazing!
Once all the important stuff has been covered in her briefing, Jess sends everyone down to the dive deck to gear up. I’m sending the divemaster trainees off on their own. “Just come back to the boat in 40 minutes time and have fun” I tell them. “If you get lost you will owe every instructor on board a beer”.
Well, everyone saw cool stuff as Jess predicted they would………………….. and the staff are still waiting on those beers from the divemaster trainees!!!!