Purification (Kitab Al-Taharah)

Dawud :: Book 1 : Hadith 83

Narrated AbuHurayrah:

A man asked the Apostle of Allah (peace_be_upon_him): Messenger of Allah, we travel on the sea and take a small quantity of water with us. If we use this for ablution, we would suffer from thirst. Can we perform ablution with sea water? The Messenger (peace_be_upon_him) replied: Its water is pure and what dies in it is lawful food.