A sit-on-top kayak hull having an elevated void in the area between the normal seated position of a paddlers legs. The elevated void which is formed into the hull of the watercraft and extends there-through to a height above the normal laden waterline generally to a level of the approximate height of the gunwales forms a hole in the craft which is surrounded by walls. Various modules may be inserted into the hull void for varying needs, such as storage modules, clear modules for underwater vision, or flotation modules. The hull void additionally allows for changes in the running surface of the kayak by insertion of rudders, skegs, centerboards or other devices The void may be left open in full or part for egress of scuba hoses, anchors or other marine devices without affecting the structural integrity of the kayak, its buoyancy, or adversely affecting its performance.