Let us be honest - you tore your calf muscle because the musculature and supporting ligaments and tendons got overloaded - not because of an incorrect swimming technique.
The one issue with swimming is that while it can be great for health, it has no ground-reactive force
(the Earth pushing back at you - yes it really does). So swimmers will lack this force during their practice. If you swim a lot, and do very little ground-based training or sports, then go try to do it (especially basketball which has high ground-reactive forces during jumping), it is much easier to overload the musculature.
The answer? Strengthen your muscles through a well-programmed weight program along with your swimming, and don't try to be an elite weekend-warrior on the basketball court if you aren't one. Remember even if you love to swim, you were built to work on land.