Re: current or ex swimmers
I'm an ex-DII swimmer, in my 40s now, and have found CF beneficial for my general strength and explosiveness. I like some of the CFE WODs for swimming, but generally prefer more traditional swimming interval workouts.
If you're a sprinter, I think you can stay fast on 2000 yds/workout if the quality and intensity are high. I'm 43 and go 27 in the 50 free and 35 in the 50 breast, both of which would have qualified me for Masters Nationals this year. I rarely go more than 1800 - 2000 in a workout, 2x a week.
Try combining some CF elements with your swimming - things like pushups, situps, squats, deep-end muscleups, etc. It keeps things interesting and intense! And it beats the heck out of 2-a-days at 10,000+!