The Crystal Detector is one of the larger Hydronauts sets. It has a suction cup gun to hold on to Green Crystal Storage Boxes and an opening storage in the rear. It comes with one Hydronaut, who has special a 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 can rotate and opens with enough room in it for a Hydronaut. There is a working compass on top. The vehicle has two arms: a claw and a clip to hold the suction cup gun.
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.