Deadlock from Crate / Oil Drum floating on water
From Worms Knowledge Base
If a game uses a map with indestructable borders on all four sides and the water level is higher than the height of the bottom borer, this glitch can be inavertantly triggered.
When a crate of any kind falls into the water, it will get stuck in the water where the bottom border would be. This could be triggered by Earthquake, Nuclear Test, or even a simple water rise in Sudden Death.
This glitch has been confirmed in Worms World Party.