Warm up
Swimmer's choice
(600/600m)
Drill
3x100 (50 kick/50 rhythm drill)
3x50 swim, decreasing stroke count by 25s
3x50 swim, descend 1-3
(600/1200m)
Main Set
1x1000 straight swim. Get your time. divide it by 10 and get an idea of what your cruise interval should be per 100.
10x100 on your cruise interval, which should be very close to what you determined by dividing your 100 time by 10.
(2000/3200m)
Last set
3x100 (50 kick/50 rhythm drill)
3x50 kick on cruise+20 sec
3x50 swim on cruise+15 sec, decreasing stroke count by 25s
(600/3800m)