Surfing Waves

Train for distance, train for speed
What I suggest trying is laps 'on time' - so lets say you are doing 25m repetitions (personally I suggest at least 50m but if 25m is what you feel like you are up to, then 25m). It takes you 14 seconds at the moment. So do 10 laps 'on 30 seconds' - basically every 30 seconds you start a new lap. So (for example), your first lap takes 15 seconds, you rest 15 seconds and push off right at 30 seconds. Next lap takes 16 seconds, rest 14 seconds, push off right at 1min. etc etc. Until you have done xx laps (6 or 8 or 10, depending on fitness). Once you get to 10 laps 'on 30' then, next session, drop the time - to, say, 'on 25' (something like 27 seconds would probably be a good drop, but trying to figure out 27 seconds after 9 laps might be a bit hard!).

This is just one part of the session - so you might do 'on time' for a block; another block might be swim 75m or 100m as fast as you can and then rest until you feel good again (breath back), then do another 75m sprint etc. Notice your times and try to beat them next time. Another block might be 400m at any pace but no stopping. If you want (a bit more advanced) do descending sets eg 4x25m as fast as possible on 20 or 22 seconds; then rest for a couple of minutes. Then 4x25m on 25 seconds and rest. Then 4 x 25m on 30 seconds.