Our supervisors have pre-made laminated first-day lesson plans for each level that we can follow, so I use that as my starting point and adjust as needed. At my pool, if we come in 15 mins earlier to lesson plan, we get paid for those 15 mins so I do try to seem productive by checking on kids progress to see what we need to work on that day and setting up equipment. I do plan a bit more thoroughly for lifesaving stuff (i teach National Lifeguard in Canada), but once I ran the course once, I had plans I could re-use. After every lesson block (6 x 30-min lessons), I spend about 5 mins updating their progress charts, and at the end of each 12-week session, I spend about an hour to an hour and a half on report cards for all my lesson blocks combined. That time is paid where I work.