The Crystal Detector is one of the larger Hydronauts sets. It has a suction cup gun to hold on to Green Crystal Storage Boxes. It comes with one Hydronaut, who has special armor light, which can be taken off and attached to the Crystal Detector. It is a ground vehicle, but it uses propellers to speed it through the watery depths. It has two Chrome Silver Harpoons and Lights/Sonar Emitters. The cockpit opens and has enough room in it for a Hydronaut. The vehicle has two arms: a claw and a "hook".
The Hydronauts defend the sea life from the evil Stingrays, who capture sea animals and Silver Crystals.
This is one of the 2 sets in which Part 412 is Trans Green.