Hello! Lifeguard here. As you walk onto the pool deck, take a glance at the pool and try to pick out a lane with a swimmer who comes closest to your pace (a observent lifeguard should be happy to point you to the lane whose occupant has been in the pool the longest or has the greatest potential for leaving soon). Have a seat at the end of the lane and put your feet in. When you are able to make eye contact or speak with the swimmer, ask to split. You can motion "split" the same way a blackjack player would. You would each then swim back and forth on your own side. Resting between intervals in a split-level scenario, just stand in front of your side. If you or the other person would prefer to circle swim, you would point your index finger towards the sky and move it in a circular motion. You would each then swim up the right side of the lane and back the right side of the lane with the lane line always on your right. In circle swimming, differences in pace are quite noticeable and sometimes frustrating, but no big deal at all if you are considerate of each other. Always wait at least 5 seconds before starting behind do another swimmer off the wall. If a lane member needs to pass another lane member, they will tap that person's foot. The swimmer in front who is being passed will keep close to the lane line on their right and allow the passer to swim out around. When you come into the wall with the lane line on your right, stop in the corner on the right side of the lane to wait out your internals. Your lane partner will flip turns with you on their right. Sometimes people are picky about sharing lanes depending on the pool. Don't let anyone bully you. Sharing a lane is no big deal or inconvenience.

Disclaimer: Now all pools are created equal. Always default to your pool's ettiquette. Definitely ask a lifeguard for tips, or for help orchestrating a split or circle share.

It is past my bedtime as I am typing this on my phone. Let me know if I can clarify anything.