Bartail gobies are usually on white sand, making them difficult to see, but this one was momentarily on a dark background.

Allie found this lionfish in a sponge.

As usual, this slender filefish color-coordinated with his environment.

I love finding these little guys. Reticulated hermit crab.

A star horseshoe worm tucked into a sponge.

You can see the eye of the conch peeking out, so this was not an empty shell. I wonder what the conch thought about being used as a sofa by a scorpionfish.

The eyes of a blue-eye hermit crab are like a beacon, luring in photographers.

I think some of these sergeant major eggs are close to opening.

I've wondered why these fish are called tobaccofish. Apparently, their coloring resembles the appearance of a cured tobacco leaf. Since I've never seen a cured tobacco leaf, I never would have guessed that.

Adult Rocky Beauties are shy, so the juveniles are super shy.

This was one of the coolest things I've watched happen underwater. I spotted an old conch shell with the point broken off, creating a round hole, about an inch in diameter. When I first arrived, only a third of red and white speckles that you can see in the first photo was . . . (Cont. in Comments)

A rough file clam has its tentacles out, ready to snag food particles floating by.

This is one of the Caribbean reef squid that Andres found on a night dive.

This southern stingray was concerned about damaging the rope coral that was in his way, even though he was in a national marine park.

I found this guy living at Paradise Reef. I've never heard the loud crack made by the claws of a red snapping shrimp, aka pistol shrimp, but I would like to.

When I spotted this guy, because he was so dark, I thought he must be an extra large Aglaja felis. But he's not! This is a dark variation of swallowtail headshield. I had no idea that they were ever this dark.

Andres found this freckled seahare.

A magnificent feather duster living in a sponge.

Spotted eagle rays are enthusiastic eaters.

Look closely, and you can see three of this sea star's tube feet.

I had a very unusual encounter with a blackcap basslet. They are usually very shy and swimming upside-down. I believe this one was guarding a nest and, he gave me quite a show.

A variety of shortfin pipefishes. Andres found an athletic one. There is a close up of one found by Almendra. And I found a lazy one.

An inquisitive porcupinefish checking me out.

This blue-eye hermit crab seemed to have a specific destination in mind.

A spotted scorpionfish who didn't like me.

A sharptail eel looking for a meal.

Star horseshoe worm living in an encrusting sponge.

A young sand diver.

Spinyhead blenny.

I found this baby bearded fireworm trudging across the open sand. About 3/4" long.

Almendra spotted this loggerhead. Looking at him straight on, you can see how massive the head is.

Channel clinging crabs are good at, well, clinging.

The interesting face and rhinophores of the rainbow sea slug that Andres found. A nudibranch, Babakina anadoni.

I love these weird guys. Slate pencil urchin. They are nocturnal, but if you're lucky you can find one in a hole during the day.

At first, I was really excited. I thought I had caught them mating. Instead, it was just a real estate dispute. The smaller red-stripe hermit crab wanted the larger house. The larger one kept pulling away, eventually walking around the corner, dragging the persistent smaller one with him.

After a brief search, Almendra was able to find the flying gurnards.

I don't see these often. It's a juvenile yellowcheek wrasse.

This is one of eight octopuses that Andres found one night. A busy night.

A white speckled hermit crab carrying around a very large house. Looks like hard work to me.

It's currently ocean triggerfish season at Cozumel with acres and acres of seagrass hosting nests. On the micro level, there is tension as females and males protect their nests. On the macro level, the calmness of space with purpose becomes a religious experience.

A star horseshoe worm choose a pretty place to live.

For having such tiny fins, this little guy was fast. (Juvenile smooth trunkfish)

A young, inquisitive sharpnose puffer.

Almendra of JUMP Cozumel is known for always wearing rabbit ears underwater. She found, on the side of a coral head, a relative.

This porcupinefish had me laughing. The more I tried to hide, the more he was determined to keep an eye on me.

Andres found a Painted Elysia doing a superman imitation, flying through the algae.

A timid goldentail eel.

This banded clinging crab dressed himself in algae for camouflage, but then he sits where there is no algae.

Portrait of a yellowline arrow crab.

I wish photos could capture the colors you see underwater on juvenile yellowtail damsels. It's just not the same.