We are aliens to the underwater world and without proper training and experience, venturing into that world would seem to be a bizarre and fearsome task. A common fear of the dark has been programmed into most people's mind because we have often been told that nighttime is when monsters and hideous creatures come out so we have to go to bed before they catch us. Put together the unfamiliarity of the underwater world and the pitch black of nighttime and you create a whole new level of peculiarity.

Let me take you there.

I have been doing night SCUBA dives since two years ago and I have always found it to be in the extremes of the diving spectrum. Being underwater is something I've already gotten used to in terms of working my gear for proper buoyancy, breathing from a compressed air cylinder, and making sure my eardrums don't rupture or my lungs don't over-expand. But nighttime is just a foreign world. It is, for starters, dark. You only get to see whatever your torch beam is pointing to. Sometimes a tiny cardinal fish will drift past my face and it will freak me out because fishes look a bit different when the sun is gone.

With one of my dive buddies, a PADI certified advanced open water diver and fellow Indo-Pacific Ecodiver, Lester (IG: @lapiskamay)

The sun sets all the difference. A lot of marine creatures love it when there is no sun. In biology, we call them nocturnal creatures and they are the main reason why I love night diving so much!

In this blog post, I will be introducing you to some of the creatures I managed to capture through my camera lens during a recent night dive. This dive happened in the last full moon and that is probably one of the reasons why we saw so many cool stuff.

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Crash Course on Nocturnal Biology

Are you ready for a crash course in marine biology?

If so, put on your thinking caps and venture with me into the majestic depths of underwater night fall.

Let's start with some particulars. To be able to do a night SCUBA dive, one has to be certified with the night diving specialty course or has to be a licensed advanced open water diver that includes the night dive course. Basically, everyone's first night dive has to be with a SCUBA instructor.

With one of my dive buddies, a PADI certified dive master, an underwater photographer, and fellow Indo-Pacific Ecodiver, Jon (IG: @imahenijuan)

All photos shown here are my own and were taken during a night dive last March 3, 2018 at Kontiki Marine Sanctuary in Brgy. Maribago, Lapu-lapu City in Mactan Island. I used my point and shoot camera, a Panasonic Lumix DMC-FT3, a shockproof and waterproof camera with Leica lens and a GPS receiver. Despite it being waterproof to up to 12 meters, I prefer to place it inside a DMW-MCFT3 underwater housing simply because I'm not taking my chances. This camera is honestly not on top of the line when it comes to underwater photography, but it was the best value I could get for a camera+housing package from a fellow diver.

I do not wish to become an underwater photographer someday but I continue to dream of becoming a master underwater naturalist who can identify marine species based on its discernible features and behavior. A camera always comes in handy when I want to take a photograph of something on a dive and then be able to compare it to species in the guide book afterwards.

My tools for species identification

Ready to learn what I've identified so far?

Let's go!

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Nudibranchs

	Willan's Chromodoris (Chromodoris willani)

A classic favorite by divers are the nudibranchs. They are a type of gastropod who, over the course of evolution and their own growth, lose their hard outer shell. They are basically snails without the swirly shell. There are thousands of individual species of nudibranchs and they vary in colors and other distinguishing features. This is the reason why they are regarded as the "butterflies of the sea". Nudibranchs span from less than a centimeter as a juvenile and up to only a few inches as an adult. They earn their colors from the varying diet that each individual species feed on. Many of them feed on stinging invertebrates (cnidarians) such as corals and hydroids, and as a result, they also garner their prey's stinging cells. Touching nudibranchs is a big no-no, because not only can they sting you, they are also relatively soft and fragile.

	Kune's Chromodoris (Chromodoris kuniei also known as Goniobranchus kuniei)

Apparently, nudibranchs don't all look the same and not all get a common English name. This hairy thing is a Phyllodesmium briareum perched on top of a piece of rubble.

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Greater Blue-Ringed Octopus

	A blue-ringed octopus with its normal pale blue rings.

At a teensy size of only up to 10 centimeters, the greater blue-ringed octopus, Hapalochlaena lunulata carries a highly potent venom that can kill a human in a few minutes. In fact, it is considered as one of the deadliest animal in the world. However, considering their size, the blue-ringed octopus moves very slowly and gracefully across the reef and often thrive in shallow sandy patches and tidal pools up to 10 meters depth. They use their toxic saliva to kill small fishes and crustaceans for food. While their rings remain pale and almost indiscernible to the human eye on a normal state, this tiny octopus would tell humans that it has been aggravated and is becoming aggressive once its rings turn intense bright blue and its tentacles curl inward. This could be an impressive sight for divers and underwater photographers as the tentacles look like little blue flowers, but always look out for this sign of imminent danger.

	Slowly becoming bright blue and then fully sitting with curled tentacles to show an aggressive state.

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Broadclub Cuttlefish

Two juvenile broadclub cuttlefishes (Sepia latimanus) one seen close-up on its side, and the other swimming away on the right side of the photo.

Meet another cephalopod on my list, the broadclub cuttlefish. Like other cuttlefish species, this guy likes to express his emotions by displaying various colors. This mesmerizing display of color bands running through the cuttlefish's body is a means to attract both prey and mate. While this species is the second largest among all cuttlefishes growing up to half a meter, these two juveniles were only about 15 centimeters. Because they move very slowly and almost just drifting with the current, divers can easily approach these attractive creatures.

A Juvenile Broadclub Cuttlefish (Sepia latimanus

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Decorator Crab

A decorator crab trying to camouflage itself into the reef's substrate.

Say hello to this stylish crustacean who puts on tiny anemones as part of his daily wear. There are many different species of decorator crabs who utilize the many things on the reef to cover themselves: from corallimorphs, sponges, hydroids, algae, and bryozoans among others. When stationary, they would seem like a part of the non-moving substrate but once they start to crawl hastily on the seafloor, you'll know it's a decorator crab. They use the 'decorations' not only to conceal themselves when hunting but also to use the stinging cells of their 'decorations' for their own protection.

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Yellow Papillae Flatworm

A Yellow Papillae Flatworm (Thysanozoon nigropapillosum)

I must admit I wasn't able to get the sharpest photo of this Yellow Papillae flatworm but I hope this one snap would give you the idea of how elegantly looking this creature was. The Thysanozoon nigropapillosum spans to about four inches with a very thin body skimming over the rock. The edges of its mantle curl into random pleats like a draping skirt. While they are as colorful and have sizes similar to nudibranchs, flatworms belong to a totally different class in marine taxonomy.

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Underwater Camouflage

Let's play a game called "spot the fish". Look at these photos and try to identify the fishes before you proceed to read the following part.

	Do you notice the fine details on this fish?

This fish's name doesn't sound so friendly, but is his personality unfriendly too?

The first fish is called a tasselled scorpionfish. The Scorpaenopsis oxycephala is an almost non-moving fish who spends its day perched on substrates with its distinct blue eyes looking out into the reef as if observing and waiting to ambush a vulnerable prey.

The second fish is a spiny stinger or spiny devilfish. Despite looking like a dull gray fish perched on the seagrass bed, the Inimicus didactylus actually possesses elegant, brightly colored pectoral and caudal fins which it would fan out as a warning sign to scuba divers or predators that disturb it. The devilfish may move around in the reef but not in the typical swimming form that we associate to fishes - devilfishes actually crawl or walk on the reef using its pectoral fins!

Both the scorpionfish and the devilfish are highly venomous. Their roughly textured bodies are covered with rows of spines and rays with varying intensities of venom. Despite them being almost motionless, divers should still look out for them as they could be aggravated or you might mistakenly step on them. Good buoyancy is very important to avoid having to be in contact with the seafloor where the Scorpaenidae like scorpionfishes and devilfishes thrive.

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Shown here is a PADI certified rescue diver, Indo-Pacific Ecodiver, Reef Check trainer, and self-proclaimed stewardess of the reef (it's me, by the way :D)

I hope you have learned something new about our reefs today. Please comment below if you want to know more and I'll be happy to answer or look them up for you.

From the colorful nudibranchs to the unapproachable devilfishes, the reef is home to millions of living organisms, many of whom are invisible to the naked eye. Even creatures that are clearly discernible should be treated with care as they too have their own defense mechanisms that could harm humans. When you visit the reef, an important rule is to never ever touch anything. Almost everything in the reef possesses a level of stinging cells so it is best to err in the side of caution. Remember, we are only visitors to the underwater world.

I hope you enjoyed the short trip to the nighttime underwater world and that you have learned to appreciate nature even more.

Stay tuned for more adventure and nature stories!

Cheers,
@xaydtrips