Swimathon

Don't know about what anyone else thinks, but it seems May is when we begin the transition to outdoor swimming?
I spotted this Sport Relief/Marie Curie event, venues all over the UK:
Swimathon
I'm going to use it as a 'training milestone' I know the longest event I've done is the 400m in an aquathon, but when I tot up the warm up/ drills/ cool downs in a training session I can easily have done 1500, so I'm now entered for the 2.5k. Well over what's required for a standard/olympic distance tri?
Nice to have targets to work towards

2.5k is along swim if you've only ever done 400 in one go before. But yeah, absolutely, go for it! I would concentrate on really stretching out your stroke and efficiency in training. Don't worry about speed at all.