Giant Clam
From AmtWiki
A type of Monster-like Terrain from Nautical Nights.
Description
Sit a player on the ground with a good-sized shield and a melee dagger (treated as a Siege weapon). Have him place the shield on his head and bend over at the waist, covering the largest possible surface area of head, shoulders and back. Place any treasure to be protected in his lap. When players come swimming near, make like a clamshell, slowly opening and closing. The arm wielding the dagger is the only legal target in combat and is “slain” after taking four hits. Giant Clams are immune to all spells, flame, poison and non-magical projectiles.