Self righting

I was recently asked what it was about the design of a lifeboat which makes it self-righting. Now,I'm not very technical but my understanding is as follows:

All the heavy stuff like engines,shafts and fuel are low down in the boat and all the light stuff, like a wheelhouse full of air are at the top. When it is upside down the heavy stuff wants to be back at the bottom and the light stuff wants to be back at the top so it rolls back upright. The newer clases (Tamar and FCB2) have cavernous wheelhouses and snap back upright quite quickly, Merseys are a bit sluggish in comparison. It's interesting in the video to see how the lifeboat sits while upside down...bow pointing right up into the air.