A person working in hot and humid environment consuming lots of plain water without salts is likely to have:
Heat cramps occur when a person is doing heavy muscular work in high temperature and humidity. There is painful and spasmodic contraction of muscles. It is believed to be due to losses of sodium and chloride in sweat. Ref: Park 21st edition page: 690.
Heat stroke
Heat exhaustion
Heat syncope
Heat cramps