It involves treading water. It is really more like soccer than swimming. Swimming speed is not all that important in water polo as the pool isn’t that big.
Some sport are complementary but most aren’t, at least at the level you need to be at to play in college. While many football wide receivers are also good at track, not many track athletes can catch a football. Soccer players don’t have the passing, fielding, or shooting skills that lacrosse players spend years developing. It takes years of bouncing that ball against a wall and catching it with a stick and there just isn’t a shortcut.
College rowing teams used to take the best athletes and train them to be rowers. Now, there are a lot of high school kids (from club teams) who have rowing experience and teams are taking them. Our high school didn’t have a team, but 4 women and 2 men got scholarships last year, all with club rowing experience.