I've seen and killed some Huge Alligator Bosses. I was at Tortuga Graveyard.
Some info about the bosses' health (which is based on huge alligator bosses' health)
Level -> Health
12 -> 4750
13 -> 5250
14 -> 5750
15 -> 6250
18 -> 7750
The health seems to increase by 500 per level, but I don't know if this is right for higher lvl bosses.I will continue looking for them.
See ya.