Water on the floor, freezer door is frozen shut.

Apparently this is not all that rare, a drain becomes clogged and the water freezes in the bottom of the freezer. My parents keep the bottom drawer fairly well stocked with frozen food so might not have noticed ice down there.

Can someone tell me how to get in there and unclog this please? The more detail the better. I can't see in there at the moment, it's frozen shut, but have turned fridge off and hope to resolve in the morning.

Thanks in advance!

Penguin