I messed up the sessions today and did session #2 instead of #1. That maybe wasn't a bad thing as the pool was quiet and so i could get on with the long routine. For the first 4 sets I managed a slight negative split across 1600m as intended.
Going into the second block my arms were tired and I set off very slowly. I managed a pace increase for 3 sets but the 4th and final was slow. I was finished!