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.
1999 LEGO Sets
1999 was a hallmark year for The LEGO Group, it was the year LEGO produced its first Star Wars theme with Lucasfilm, beginning a trend of licensed LEGO products. This event came alongside the year that Star Wars Episode I: The Phantom Menace was released reviving the Star Wars franchise. Along with the successful Star Wars theme being introduced, LEGO released Rock Raiders, Slizer/Throwbot and Winnie the Pooh. In addition, Ice Planet 2002 and the Spyrius theme was re-released. A number of themes were discontinued in 1999 which included Cyberslam, TechPlay, UFO, Insectoids, Znap and Model Team.