I was viewing the water in the ocean when i saw that skeletons seem to be nearly jumping out of the +3 block deep water not anywhere near land and setting on fire. They then go back down and repeat.

How to reproduce
1. make an area of water deep enough that mobs must float
2. spawn a skeleton//zombie in it
3. Make sure it's morning
The skeleton or zombie will jump out of the water while they float causing them to momentarily burn.