the Prophet said: "Let none of you urinate [in still water, then perform Wudu with it."1
Jami` at-Tirmidhi Book 1, Hadith 68
← Previous Hadith "I heard AlIah's Messenger while he was being asked about water in open areas of the land, and predators and beasts come to it." He said: 'So Allah's Messenger said: 'When the water is two Qullah it does not carry filth.'"

Jami` at-Tirmidhi Book 1, Hadith 67 Next Hadith → "A man asked Allah's Messenger 'O Messenger of Allah! We sail the seas, and we only carry a little water with us. If we use it for Wudu then we will go thirsty. So shall we perform Wudu from the (water of the) sea?' Allah's Messenger said: 'Its water is pure, and its dead are lawful.'"

Jami` at-Tirmidhi Book 1, Hadith 69