While many fish naturally breathe underwater, some creatures (or when using the human model in modded versions) have oxygen meters. This removes that restriction.
: Using mods in online modes can lead to bans or disconnects; it is best to use them in single-player "Survival" or "Great Swamp" modes.
The Feed And Grow Fish mod menu is not a sign of weakness; it is a tool of creative expression. Whether you want to roleplay as a benevolent giant protecting small fish or a hyper-speed piranha stripping the ocean bare, the power is in your hands.