Aquatic

The term Aquatic refers to an in-game group of mobs that live in oceans and rivers and are able to swim.

In Java Edition, aquatic mobs obligatorily share the property of being in the aquatic entity tag. This also causes them to take extra damage from the Impaling enchantment and being able to survive in land with the water breathing effect ‌[BE only].

Some or most aquatic mobs may also take suffocation damage when on land, not cause pufferfish to puff, and not take drowning damage, although this doesn't affect their classification.