I don't do swim laps, but I do do flat road laps... we have 1km of straight road before the hills begin, so when I want a recovery ride, I go out and do "farm flats" which is a 1km false flat rising toward town, turn and back to the gate.
I also do hill reps on a 1km long medium rise.

I find it very hard to keep a track of how many - numbers just get muddled.

So i do something similar to KSH's suggestions. I have five children and and eleven nieces and nephews... so I work out how many laps/reps I intend to do, and then chose a combination of families so I have the right number of children to match the laps/reps, and then I ride... each stage for one of the kids... I usually order them youngest to oldest by family and I never lose track...

"This ones for Em, this ones for Em... ok, that was Em's, this must be for Becca..."