Does swimming and mountainclimbing in contrary with?

Does swimming and mountain climbind in contrary with each other? i do both and even some workouts on my stomach to reduce its fat but the lifeguard said you can't make progress in your swimming this way. those sports made youre body hard while swim needs a soft body. i want to know how true is it? and Shoud I stop these? I mean my coach said my body in water is not that much relaxed. He said i constrict my muscles during swim (swim likes a robot; he said). and he said it is because of montain climbing and other activitie which i do , they made my muscles compressed while swimming needs relaxed ones. also I am not so sure about his opinion maybe my problem is somethin else? i will be glad to hear you opinion