I've been swimming again this morning - I felt so good after 20 lengths that I did another 5. I've just confirmed that my local pool is in fact 33.3 metres long rather than the usual 25 or 50, which means I swam over 800 metres (which used to be my standard daily swimming distance). It also explains why my length time is over a minute.
I'm thinking of entering the
swimathon in April - gives me something to work towards.