I have some sympathy this with, though I get that 'slow', 'medium' and 'fast' will always be relative terms depending on who's in, and if there are a load of slower people in then in the interests of making the most of the available space you might find yourself sharing a faster lane with someone who's slower than you. I (faster than a turtle but slower than a barracuda - a porpoise maybe?) have given feedback a number of time to lifeguards on duty, the people on reception and also online, and nothing ever changes, even when I've complained about the way faster people will sometimes swim in slower lanes and try to intimidate you out of the way or 'accidentally' push you. I wish they'd listen as it's very off-putting. I'm not suggesting the OP is one of these but it's a public pool and some people act like they have priority, which is just bad manners. While we're at it, it would be pleasant if everyone could remember to shower before they get in...