The Water-based life form, also known as simply Water lifeform, was a form of intelligent lifeform which resembled water in both its liquid and gaseous form. They lived on a planet which held the ruins of an ancient city, covered in what appeared to be water but which was actually many lifeforms.
While Russia was running their own Stargate Program, they sent a single team to the planet with a Mini-Sub to investigate the ruins of the city and to return with a sample of the water, which appeared to be generating heat. After returning to Earth with this sample, however, several of the Russians were taken over by the water lifeform in an attempt at returning home. The lifeforms were not malevolent and while they did initially prevent Doctor Daniel Jackson, Major Samantha Carter and Doctor Svetlana Markov from returning home and possessed Teal'c, they did not harm them and according to Teal'c had no wish to do so. (SG1: "Watergate")