This mods aims to expand a bit the ocean fauna, adding ten new water creatures and a new biome, along with some other blocks and items.

New update trailer:

The new mobs:

The Anglerfish: It spawns quite often in deep oceans and is aggressive towards other smaller fishes. Its meat can be used to get a new light source.

The Coelacanth: It spawns very rarely and only when it's raining in deep ocean dunes. It can sell for a lot of emeralds.

The Isopod: A water arthropod that only spawns in the new biome. Its meat can be cooked or used in a new brewing recipe.

The Horseshoe Crab: Another water arthropod that spawns in beaches near the water. It drops its thorax, which can be used in another new brewing recipe.

A giant spider crab

The Giant Spider Crab: These passive crustaceans will spawn in cold oceans. They'll roam the seafloor and can dig up stuff from the sand if they're underwater. The stuff they dig up depends of the type of sand below them (more info here). They can breed if you feed them almost any meat, dropping crab eggs which you can use to spawn baby spider crabs. They drop crab legs which you can eat raw or cooked.

The Ghost Shark: A deep sea fish that comes in 4 different variants. They're venomous but passive creatures, and their meat can be used to get their stings, which are consumables that give a long lasting poison effect to other mobs.

The Mudskipper: These are small but territorial creatures that wander the swamps near water. They jump around to impress each other but they get alert if you get near them. You can also find blue alpha mudskippers. These try to fight any other alpha they find to protect their territory and If one ends up killing another they'll drop their fin.

Deep Sea Fish: These ambient fish live in the Deep Ocean Dunes and prey on each other. There are 4 different sizes and 11 different species in total, and they drop deep sea fish meat.

These species are: Sabertooth Fish, Velvet Whalefish, Grenadier Fish, Hatchetfish, Fangtooth Fish, Dragonfish, Telescope Fish, Viperfish, Lantern Shark, Flashlight Fish and Pearleye Fish.
Squat lobster variants

Squat Lobsters: They are friendly and curious animals that come in 7 colorful variants. You can find each one on a different ocean biome and they drop their tail once dead.

List of the species here.

The Sea Pig: A rare sea cucumber that spawns on the bottom of the deep ocean dunes. If they spend around 30 minutes feeding over sand or gravel they'll secrete a slimy substance along with some particles. Then if you right click it, it'll give you the new Poison Protection effect for 15 minutes. You can also use its meat to try to get the effect by eating it raw (1 in 5 chance) or to brew a potion. If you're lucky you'll find one carrying a baby spider crab on its back.

The new biome:

Deep Ocean Dunes: Here you can find a new type of sand, two new animated blocks and a new particle emitting block. If you dive deep enough you won't be able to see much.

The new blocks:

Deep Sand: A type of sand that only generates in the depths of the Deep Ocean Dunes. It can be crafted into all the sandstone blocks you'll expect

Giant Tube Worms moving

Giant Tube Worms: A new animated block that only generates down below the Deep Ocean Dunes. It can only be placed on deep sand.

Anemones

Anemones: A glowing anemone with animated texture, you can collect them with shears and they give a poison effect when touched.

Hydrothermal vents

Hydrothermal vents: A block that generates smoke if underwater and at a certain depth. It also has custom sounds.

There's also a new painting.

Items and recipes:

Each mob can be put in a bucket (baby spider crabs too!) and has its own drops. The fisherman villager has new trades too! Here are the main recipes.

Food Recipes:

Brewing Recipes:

The sinking effect will make you sink to the bottom if you're in water or lava. Only works in survival.

The healing vigor effect will add 2 hearts and 4 saturation points every once you consume an item.

Brewing mudskipping potion

The mudskipper potion will give you the leaping, haste and weakness effect at once. It can be upgraded to a longer version with redstone. (The bottom row are leaping potions)

Long posion brewing