As we all know, cardio and strength training have completely different effects on your muscles, and your body's response to them. Strength training trains the body to make those big anaerobic muscle fibres, giving you the body-builder look, but cardio builds endurance muscles without hypertrophy. (Why does cardio/aerobic exercise lead to muscle loss? has a fuller explanation for anyone new to the site.)
When I swim, my breathing is restricted because of the water (let's say my technique is poor), so an intensity of exercise that's normally aerobic for me becomes anaerobic instead. I feel out of breath (the sign of an oxygen deficit) after a sprint that doesn't tire out my muscles: if I were on the bike instead, I'd be able to keep up that level of activity for hours.
So my question is this: how does an anaerobic exercise (my swim sprint) compare to an aerobic exercise of the same intensity (my bike ride)? I'm looking in particular for the effect it has on the muscle profile: the fat-burning effects are already covered by do low oxygen levels effect fat burn and/or muscle strengthening? and Does the amount of breathing (holding breath/breathing fast) affect the calories burned during a workout (not heavylifting)?