If you had a large interceptor vest with medium plates....You maybe be able to stay afloat if enough air gets into the excess room, but I don't recommend gear that doesn't fit exact to you. Also if you have a lot of waterproofed bags that have not been compressed down like cryo-vac it's possible but I wouldn't try it personally. As for your gear being dumped, drop all the unnecessary stuff and keep only the mission essential equipment. If that's all you got, well.....you better swim hard and get to one side or the other
. Don't panic or it's game over!!!
Just my 2 copper colored coins,
DW