At the beach and in the swimming pool, avoid reckless jumps
Do not dive headfirst without checking the bottom and depth of the water. Never dive into unknown areas of little depth, especially from high heights. This includes areas where there may be stones or branches.
Even if you go to the same beach all the time, check that the currents have not changed; where there was quite a lot of depth last year, could now be a sand bank.
Check that there are no other people swimming near you and be careful not to bump into them. A reckless jump can lead to serious consequences, even a spinal cord injury, for you or other people on whom you may fall onto recklessly.
Beware of belly flops as well. Even if they seem harmless, they can cause more than just a mere bruise. A belly flog gone wrong can cause internal injuries to the abdomen that can be very serious.