Recreational water environments can pose various health risks. The most severe danger is accidental drowning. Another source of harm is injuries caused due to slipping, tripping, or getting entrapped in ladders, drains, or other fittings. 

Ship sanitation is also important as swimming and spa pools can transfer infectious diseases such as diarrhoea, and skin, ear, eye, and upper respiratory infections. Hot tubs and whirlpools can provide a suitable environment for the growth of Legionella and Mycobacterium spp. Pseudomonas aeruginosa is also present in whirlpools, leading to skin infections when pool design or management is poor.

Swimming and spa pools can be contaminated by pathogens transmitted through the faecal-oral route, which can enter via human sewage or animal faecal contamination or are released directly by infected bathers. One such pathogen is Cryptosporidium spp., which can survive even in the highest levels of chlorine used for maintaining residual disinfection in pools.