My swimmers enjoy sessions like these where we get a nice aerobic workout with a decent amount of distance covered, but without making it feel like a long slog. The shorter set sizes makes it easier to handle mentally if you are struggling physically. The session is meant to be run straight through without stopping between sets. The times are there as a guide and should be adapted for whatever the swimmer would use for an 80% effort workout. Notes are colour coded for the part they apply to.
Of course the usual disclaimers apply, this is an example of my session made for me, you are free to have a go or adapt it, but do so at your own risk & under your own responsibility etc.