Sunan Ibn Majah Book 1, Hadith 123
"The Prophet went out to relieve himself and when he came back, I met him with a water skin and poured water for him. He washed his hands and his face, then he went to wash his forearms but his garment was too tight, so he brought his arms out from underneath his garment and washed them, then he wiped over his leather socks, then he led us in prayer."
The Prophet was asked about seawater, and he said: "Its water is a means of purification, and its dead meat is permissible." (Hasan)
Another chain with similar wording.
"I brought a basin of water to the Prophet and he said: 'Pour it,' so I poured it and he washed his face and forearms, then he took fresh water and wiped his head, front and back, and then he washed his feet. He washed each part three times."