Tear off door 23 to find the Salt Wyvern.

A giant sea serpent that haunts The Endless Sea. Though not taxonomically a wyvern (only dusty old sods reading dusty old books in the dusty old halls of Grift's ancient universities actually care for that shit) folks have called it one for too long not to anymore. 

Where it swims, dead and dying fish float in the water's foam. A risky harvest.