The bug

Bees will take damage in water every 0.5 seconds, regardless of the value of the Air: tag. This can be reproduced by spawning a bee under water with a spawn egg, or with the following command:

summon bee ~ ~ ~ {Air:300s}

Note that the bee won't take suffocation damage if spawned with NoAI:1b, but may drown as usual.

Original description

Upon contact with water sometimes a bee takes damage. This is best reproduced if you create a superflat water world and summon a bunch of bees above water and watch as they move around.

Could be related to MC-167147 I found both at the same time.