Nile Monitors (Lequaan in South Africa) are awesome! My friend used to work at a pet shop, he got called to someones house because one of these things had invaded the swimming pool, and attacked the cat...The people weren't very impressed, but we thought he was awesome!!

As aggressive as they can be, they still run like banshees when a big Fish Eagle, or the likes is around. Fishing at a dam once I hear a weird noise, and one of these guys, not a very big one, but big enough, came bolting out of the bushes, and launched himself into the damn. The dam was about 3 meters lower than the banks, because of a drought, and the lizard had quite a bit of "hang time" before he hit the water. When I looked around, I noticed a very large Eagle circling around, so I figure this thing was making a hasty retreat!

Your one is awesome, hopefully he'll overcome his posturing and hissy-ness, lol!!