You've built yourself a wonderful-looking LEGO mad scientist island lair surrounded by shark-infested deep waters. Now, all you need is a proper coast guard ship to patrol your shores. The LEGO Coast Guard Patrol should do the job nicely.
The LEGO City Coast Guard Truck with Speed Boat is a medium-sized LEGO playset intended for children aged 5-12, and part of the 2008 City series of playsets. With 361 pieces, the set is used to construct a coast guard truck, trailer, and speed boat that can sit on the trailer. The boat has a winch so that it can be "launched", and it does actually float, so can be used as a water toy. The set is designed for use with other City-themed playsets. It includes two figurines, a truck driver and boat pilot, and the boat pilot comes with a life jacket.