Seal

Dogs are useless underwater, and axolotls can't be tamed, so Minecraft needs a true underwater wolf: the seal. They'll spawn in frigid oceans, be tamed by salmon, and serve as loyal bodyguards, swift in the water but clumsy on land. They should also have their own armor; I suggest "Flipper Armor," crafted from 1 Copper Ingot, 1 Turtle Shell, and 4 Prismarine Shards. This armor will protect against Guardian spikes and increase their underwater breathing time. This maintains the game's balance: axolotls remain "pocket healers" that fit in buckets, while sea lions become tough, permanent protectors for exploring the ocean depths.