As per MC-255199, which is an intentional behavior, Bees don't instantly incur damage upon contact with water. Instead, there's a brief delay before they begin taking damage. However, this countdown is reset when the world is reloaded. Consequently, upon reloading the world, Bees will experience the delay before taking damage again, even if they were already taking damage before the reload. The issue lies in the fact that this timer isn't saved to NBT.
Attachments
Comments 4
steps to reproduce
Summon a bee and a blaze underwater
Rejoin the world
Observed: The bee momentarily does not take damage from the water, even though it had been previously damaged by the water before the reload.
Expected: The bee should promptly resume taking damage, similar to the blaze, since it had already been affected by water damage before the world reload.
Relates to MC-59626, MC-69821, MC-234389, MC-257420, MC-254131, MC-257419, MC-260236, MC-254135 and MC-268972.