The Aquasharks were villainous underwater miners who competed with the Aquanauts for control of crystals and crystal mines and appeared in sets from 1995 to 1996 and again in 1998.
Aquazone was an underwater theme introduced by LEGO in 1995 that lasted until 1999 and contained five subthemes all of which took place in the ocean and typically involved two sides fighting each other for valuables such as Hydrolator Crystals.