Do not get over-zealous at the gym lifting upper-body (bench press, decline & incline press) the day before a swimming workout. Not only does it make your entire upper body sore, it makes it extremely difficult to do swim sprints the next day. Yes, I know you went to bed early (9:30) to try and give the body some ample time to recover, but it didn't happen. Loud snoring and drool (according to your wife) does not equate to quality recovery time.
So even though you managed to eek out 6 x 250y pyramid sprints (plus 500y warm up), you could have done more if you weren't hurting so much. Be smarter next time.
Thanks for listening,
P.S. Also make a note not to talk to yourself in a public forum ever again. Thanks.