So I've spent the last 9 weeks learning the breast stroke and freestyle. I've got the techniques down. Problem now is, after every 25-50 meters, I have to stop to catch my breath. Would love some advice from a good swimmer.

Is this normal? I can run 7-10 miles before I'm tired, but after a lap or two in the pool, my heart rate's blasting and I need to pause for a minute or two. Will this eventually improve? Any advice?

Would really appreciate it.