Swimming stops being monotonous with people

Swimming alone is looking at a black line for forty minutes. It's the sport with the least distraction of any of these, which is why it's the one most abandoned in January. Sharing a lane and a set changes the whole length of the session.

How a pool session gets organised

The timetable outranks everything
The pool opens when it opens and the lanes fill when they fill. A swim session is organised around the pool's hours, not the other way round.
Sets go better two by two
Someone leaving five seconds ahead of you is the difference between finishing the session and cutting it short. You don't need to swim the same: you just need not to swim alone.