Tutorial:Dolphin farming

There are at least two purposes for which you may want to farm dolphins. One is for use as transportation: getting plenty of spare dolphins to swim with as per Tutorial:Transportation methods § Dolphins. The other is for killing for cod, becoming a style of fish farm. This latter purpose has a long history of getting patched by Mojang, so beware that any dolphin farm described here may stop working in the future.

Relevant facts:

• Dolphins spawn between y=50 and y=64 inside water in most ocean biomes.
• Dolphins spawn best in regular ocean and deep ocean. Even there, they share the water creature mob cap with squids and nautilus, which is 5 on Java Edition.
• (Dolphins used to drown themselves: MC-306840 fixed in 26.2)

A dolphin farm shares many traits with an oceanic squid farm. You find a relatively small ocean and remove all water within 128 blocks distance using sponges, a Moses or other methods. Then build a vat of water at y [50,64], and an AFK spot high above.

Methods of killing may involve lining the vat floor with magma, or making a soul sand bubble column sending the creatures up to the AFK spot, trapping them there inside cobweb for the player to decide what to do with (e.g. save and nametag the dolphins while killing the squid).