On a recent trip to Maui, we only saw the heavy and slow rotomolded sit on top kayaks by Ocean Kayaks and similar brands. We wondered how cool it would be to have a high performance touring sit on top kayak for tropical waters for offshore adventuring or rock gardening. Here's a few that would be ideal for the task..
French company RTM makes some great boats and wave skis. Their Midway and Disco+ kayaks both have one enclosed hatch, a well in the stern for gear and thigh straps for rough water handling and surfing. http://rtmkayaks.com/products/sit-on-top/disco
Necky Kayaks recently unveiled the Vector 14 which has two enclosed hatches and one open well. Like the RTM boats, you can attach thigh straps for better control in bumpy waters. More info:
-Emotion Grand Slam 14'
-Wilderness Systems Tarpon 160
One issue with all the above models is weigtht. The Tarpon for example is 76lbs. Know of a composite model?