I am a stronger swimmer than runner; used to swim competativley when I was younger and still train 3 or 4 times a week. I think the secret to swimming like running I imagine, is technique. A good place to start is with Terry Laughlin's Total Immersion (Google it) method. It concentrates on core body strength, front quadrant and being slippery.
Also PM'd you with a good link where you will get loads of swimming advice and tips:d