[LockDoc]

-
Here is what the back of the lock and latch looks like.

If you can see the latch and the lock pawl is not blocking it you should be able to use a tool with a hook on the end of it to push the latch down and unlock it. I use a long cotter key removal tool. Spray it all with penetrating oil first. I usually drill a 3/4" hole in the bottom of the tub so I can pull the latch down.