From Monkey Island wiki
Rum Rogers Sr. was first mate under Captain Marley on their fateful quest for the legendary treasure of Big Whoop. He died some years later in his cottage on a small island just off Phatt Island while having his bath. His skeleton was found by Guybrush in the cottage basement. True to his name, Rum had a strong affinity for rum.
Like the other members of Marley's crew, Rum Rogers held a piece of the map that led the crew to Dinky Island, resting place of Big Whoop. After LeChuck's transformation into a ghost he systematically hunted down and killed each of Marley's crewmen. Aware of Rum's tendency to toast bread while taking a bath, LeChuck simply dropped the electric toaster into the bathtub with him.
When Guybrush finally discovers Rogers' body, in a secret room in his house on Phatt Island (now owned by his son Rum Rogers, Jr.) his skeleton is still sitting in the bathtub, clinging to the map-piece. The map-piece seems to be stuck to his decayed skeletal hand as Guybrush snatches them both.