Swimming To Tone Stomach?

I'll take the last part first: I train in triathlon so yes, its okay to swim straight after cycling. I believe you might benefit more from cycling first since your heart rate will already be raised from biking. The more time spent in the pool will speed up the results. But the sets have to be quality, although there is something to be said for quantity. Depending on ur fitness, start off with distance (Ex: I'll do 500 yards no matter how long that takes) and work your way up to a mile (about 1750 yrds). Then you can focus on time and shortening the time it takes you to complete the work out. I'm saying to work on distance then time because swimming, for lack of a better explanation, is an art. You have to feel your way through the water (it is very much technique driven) but since ur getting BACK into it you know that. Focus on time later.