Swimming

I would avoid just ploughing up and down.

Swimsmooth.com has a load of set you could try.

An easy set to follow would be

4 x 100 warm up (4th length anything but fc)
4 x 100 drill sets of choice - catch one day, roll the next, recovery etc...
8 - 12 x 100 or 4 - 6 x 200 off whatever your threshold pace is - I'll do 100 off 2 minutes, my threshold pace being 1:25
2 x
100 warm down

As long as you don't warm up on breast stroke.