I was making a track with rails and I went off the track with my minecart and onto some ice. I click the cart while I'm in it to destroy it and I either go through the ice to the water under it or go into the ice and can't get out unless I fly out.
Steps to reproduce
1. Ride a minecart on to some ice
2. Look down and click the mine cart and you are underwater or in the ice. (Depends on if you are in the flying mode or not)