Below is a simple Notion training database, just enter the distance swam in km, length of session in minutes and the rate of perceived exertion. ( score yourself on how hard the session was 1-10. 1 being really easy 10 being very difficult). Modified Borg scale. The stress score is how hard the session was, over 7000 is very difficult and will take some time to recover from.
Keep a track of how many difficult sessions you do each week and look at how many recovery sessions you are doing.
Training needs to be a balance of hard sessions and recovery sessions.
You can replicate this page by clicking three dots on top right and clicking duplicate. (It’s free)
You can also use something like my fitness pal or strava