Aquazone

LEGO Aquazone was a LEGO theme which ran from 1995 to 1998, following the idea of deep-sea mining and exploration. The storyline revolved around opposing groups of deep-sea explorers and divers competing for the natural resources the sea floor had to offer. Along with undersea mining, the resources they sought were "hydrolator crystals", shiny silver crystals with ambiguous properties.

Throughout its run, Aquazone featured a number of split factions all going for the crystals. The Aquanauts, Aquaraiders and Hydronauts were the protagonist groups, and were opposed by the Aquasharks and Stingrays. The line sported quite a diverse range of sets over the years, including two-wheeled car-size submarines to drive along the ocean floor, various vehicles with magnet or pincer tipped gooseneck style arms, and submarines built to look as closely like giant sharks/rays/crabs as possible. Rule of Cool indeed.

A total of 28 sets were produced for the Aquazone line over its years of existence, the bulk of which were made in 1998. Compared to some of its contemporaries, such as LEGO Adventurers, it's actually a surprisingly small figure for such a longevous theme.

You can take a look at the various sets here.

Tropes used in Aquazone:

 * Animal Mecha : The Aquanauts and Aquasharks had relatively realistic submarines, but often heavily inspired by the body structure of various marine creatures. The Stingrays took the animal motifs even further and their subs had a far more pronounced naturalistic shape.
 * Colour-Coded for Your Convenience: Sets belonging to the same group normally shared basic colors, color-schemes.
 * Detachment Combat: The larger subs of the Stingrays had the ability to separate into smaller underwater crafts.
 * Enemy Mine: An Aquazone-themed comic in the LEGO Mania Magazine had the Aquanauts and Aquasharks teaming up against the Aquaraiders.
 * Everything's Even Worse with Sharks : The Aquasharks, the first badguy faction. Fittingly enough, they had shark-shaped submarines and often kept sharks as either pets or trained attack drones (how ever that worked...).
 * Everything's Squishier with Cephalopods: Many sets came with octopuses. They usually guarded the crystals, but at least one comic depicts one helping the good guys.
 * Evil Is Cool: Well, In-Universe, one could argue... The design team clearly put more effort into designing more interesting and unique set designs for the Stingrays and Aquasharks than they did for the heroic factions.
 * Hook Hand: Some of the antagonists had a translucent green one.
 * Informed Attribute: The American LEGO Club magazine once said that the Stingray characters were terrible sub builders, despite the awesomeness of sets such as the Sea Creeper and the Stingray Stormer.
 * Power Crystal: Speculated to be one of the uses of hydrolator crystals. In some countries, they were explicitly stated to be energy crystals. Amusingly, they used the exact same crystal piece as the later Energy Crystals of Lego Rock Raiders.
 * Rule of Cool: Seriously, submarines shaped like sharks and rays.
 * Science Hero: The Aquanauts/Hydronauts, who were defined as the good guys, researching marine life and protecting the seas from the Aquashark and Stingray pirates.
 * Sigil Spam: All the factions had at least one or two large logos of theirs on any given sub. The Aquanauts in particular.
 * Spider Limbs: Subs generally used flexible arms to grab stuff. They were equipped either with claws or functioning magnets.
 * Spiritual Successor: 2007's LEGO Aqua Raiders and 2010's LEGO Atlantis don't bear the Aquazone subtitle, but are clearly in the same vein. Aquazone itself is sort of a Spiritual Spinoff of LEGO Space.
 * Sub Story
 * Submarine Pirates: Both badguy factions, the Aquasharks and Stingrays.
 * Under the Sea
 * Underwater Base
 * X Meets Y : SeaQuest DSV meets Aquanox AS A LEGO THEME !