Marty serves as one of the two principle divers on this South African adventure, the other being his best friend Sammy, whom he met in dive school. He is responsible for ensuring the underwater pumps are working properly at the bottom of the ocean and scouting diamond hot spots. He and Sammy are the young, fun, troublemakers of the crew, often rebelling against Captain John's authority. House hopes to find diamonds so he can use the money to travel and provide for his mother, who is a single parent.