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.
1998 LEGO Sets
In 1998, LEGO released several new sets and themes, including the LEGO Star Wars theme, which was based on the Star Wars movies and featured models of characters, vehicles, and locations from the films. This theme was extremely popular and helped to boost LEGO's sales and popularity. 1998 was also the year that LEGO introduced the LEGO Mindstorms theme, which was a line of sets that allowed users to build and program robots using LEGO bricks and a computer.