Out of my lane please!

It is difficult to find good places to go swimming. During the summer just a couple miles from my home the city pool has 2 lap lanes roped off. I buy a summer pass so I can get as much swimming in as I can. Yesterday was a mess. 4 girls hop into the lane and leisurely swim - well, I'm trying to lap swim and the sign says "Lap swimmers Only". The lifeguards didn't do anything so I kindly asked them to leave. Then, I'm almost done, just warming down when a kid dives into my lane and almost hits me - hello! This is not a diving lane, this is a lap swimming lane. I spoke to the manager of the pool afterwards to let him know the lifeguards need to keep a better handle on the kids so the lap swimmers don't get hurt.