Spawn Point: Anniversary Island
Find a flat-ish spot on the beach, as close to water as possible.

Mudpuppy reduces your oxygen use by 50%

Air Jars are useful for long journeys under the sea!
Each Air Jar fills your oxygen multiple times.
Air Jars work on other players and dinos within the area.

Both wild and grown Plant W Plants provide Oxygen and Stamina Regeneration. You can sprint forever as long as you stay within range of a Plant W.
Does not work if you are not swimming; such as boot weights or hydrosphere.

There are 5 Zones based on your elevation.
Surface, Low, Medium, High, Crushing

Pressure Sickness: Level 1-3
It causes you (and dinos) to move very slowly and deal much less damage. You get it by quickly changing pressure zones, even by bed or teleporter. It goes away slowly as you spend time at that pressure zone.

Pressure Acclimation: Level 1-3
If you spend enough time in your pressure zone then you will get a boost to XP Gain, Stamina Regen, and Damage.

They spawn on beaches and in reefs.

Easy to kill with a tool or dino. I let them catch my dolphin and eat them.

Harvest their bodies with a pick for easy Paste and Black Pearls.

Tame them for passive pearl and black pearl generation.

Put manganese in a forge with Charcoal and Metal Ingots to make Hardened Steel Ingots, which are used for a lot of Aquatica stuff.

Crystalized Wood can be found in many places at the bottom of the ocean.

Barnacles are found along cliff sides and extinction structures.

The Dunkleosteus has always been the OG of water farming.

This roaming island-crab has a lot of farmable element. Bring a pick and avoid lava vents. The island-crab teleports in and out of existence, and slowly moves around the ocean surface.

An underwater lake? No! It is the entrance to The Abyss! It is the lowest part of the map. Make sure to have parachutes, a tek chest, or use the ramp at one end of the "lake".

The abyss is covered in dangerous creatures, including Rexes, Yutyrannus, Reapers, and Shadowmanes.

Abyssal Creatures do not have oxygen stats, meaning they will not drown.

Abyssal Creatures can walk underwater. Toggle this ability on or off by looking at the creature and holding E, or while riding it hold R.

Abyssal Reaper Queen behaves exactly the same as other reaper queens. Use similar methods as to get a normal reaper king.

Abyssal Creatures:
Alpha Rex, Anky, Moschops, Procoptodon, Reapers, Rex, Stego, Therizino, Thylacoleo, Yutyrannus