Did 1k in total. Didn't die. 6 x 100m sets (eagerly started out at 1:38 but that soon dropped to 1:50 for the rest of the session) and a couple of 200m efforts just to pile on the discomfort on top of the lack of swim fitness.
Only 3 others in the lane at most, the pre-9am sessions are long booked up but the ones during the day are sparsely booked. Which is nice.
Have more sessions booked for the rest of the week. Aiming to squeeze in 20k in the remains of April by doing 1600m each weekday.
I'm a long way off a CSS of 1:30.