Transmission problems??

I posted a question the other day regarding my circulating pump. Well I believe the problem is in my tranny. We were out the other day and I got in the water. As soon as my friend went to take off, the boat hesitated and started to bog down, wouldn't plane out and there was a loud bang. I got in the boat and we were unable to get on a plane. I ran the boat in my driveway and when it is put in gear there is a loud noise coming from the tranny where the shaft goes in. This noise starts out quiet at first and then builds after a couple seconds. But the boat goes in and out of gear with no problem. Any ideas what the hell is going on here. my guess is that we hit something underwater (the bang noise) and the shaft was bent causing us to not be able to get on a plane, hence the loud vibrating noise coming from the tranny. I know it is hard to describe but any input,costs,parts would be great