How it works

Two mechanisms, deliberately layered:

1. Primary — reset the timers. A dolphin dies from two independent countdowns: its air supply (it breathes air, so it drowns if it can't surface) and its moistness (2400 ticks, which drains when it's out of water). Every 2 seconds the plugin refills both on every loaded dolphin, so neither ever reaches zero.
2. Safety net — cancel the damage. An EntityDamageEvent listener cancels DROWNING, DRYOUT, and SUFFOCATION for dolphins, in case a timer slips through between top-ups (e.g. right after a chunk loads).

Plus: dolphins are marked persistent (setRemoveWhenFarAway(false)), because by default they despawn when no player is nearby — which would otherwise empty your tank while you're away.

Timers are refreshed on EntityAddToWorldEvent too, which fires on both spawn and chunk load, so a dolphin in an unloaded aquarium is fine the moment it loads back in.