The bobber of fishing rods sometimes float above the water. After testing a few times, it seems around 50% of the time it will float around 1/4 of a block above the surface of the water.
This also happens when tried on land as well.

This does not affect the behavior of fishing, but it does have a tendency to look off.

To reproduce:
use fishing rod, swim at water level. the bobber will occasionally be above the water.