Aquazone

Aquazone was an underwater theme introduced 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. Aquazone was the second new theme after Pirates that was introduced after the initial three classic major themes Town, Castle, and Space from 1978.

Aquanauts
Aquanauts was the first subtheme in the Aquazone theme from 1995 to 1996. The story consisted of the Aquanaut miners, a group of miners based at the Neptune Discovery Lab, fighting against the villainous Aquasharks and their leader Thresher for control of the crystal mines. The first generation of sets consisted of a yellow base color to the subs which gave the Aquanauts a more realistic appearance to real submarines.

Aquasharks
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.

Aquaraiders
The Aquaraiders subtheme started and ended in 1997 and was the descendent of the Aquanauts and Aquasharks subthemes when these were discontinued. The Aquaraiders where an alternate villain faction that competed with both the Aquanauts and Aquasharks and consisted of three vessels in black with green accents and trans-neon green window pieces. The ships had accessories that looked like drills and grinders and had an exotic look for submarines.

Hydronauts
In 1998 and 1999 which was the tail end of the Aquazone theme featured the Hydronauts, a story line that involved a battle between the Hydronaut miners and the fish-like Stingrays. The set's color scheme was similar the one of the Aquanaut sets but was different in that the transparent pieces which were now exclusively transparent green instead of blue and trans-neon orange. The Hydronauts minifigures had unique masks printed onto their faces which gave them a very alien look.

Stingrays
The final Aquazone subtheme in 1998 was the Stingrays, which were fish-like mutants and enemies of the Hydronauts who used underwater vessels that resembled sea creatures. The villains included Commander Manta Ray and Raven Ray and the subtheme contained 5 sets and set 6109 Sea Creeper was the same as set 6140.