Agree, sinking to the bottom when in ragdoll needs to be addressed, however I believe initiating ragdoll when you eject from a fast moving vehicle is a feature.
For example: ejecting out of a moving land vehicle can cause you to ragdoll and cartwheel down the road which is what would happen in real life. Ejecting from a speed boat also has its drawbacks however not to the extent depicted in the game at the moment so yes it needs to be tweaked.