Is it a polluted? Although the water may appear to be idyllic, take a moment to consider is anyone else swimming, are there fish or other wildlife drinking and living there, are there any strange smells or coloring. Research the beach that you are visiting, certain beaches in Rio de Janeiro for example has pollution levels that are dangerously high. Also, look for sewerage outlets nearby that may be contaminating the local stretch of beach.
Please read the originial post here: https://exploresecuer.travel.blog/2020/08/17/the-most-preventable-killers-of-healthy-travelers-abroad/