Sayyiduna Abu Umamah (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "The martyr of the sea is equal to two martyrs of the land. The one who is seized by (sea)sickness at sea is like one who rolls in his own blood on land. (The time spent) between two waves at sea is like one who spends the whole world in obedience to Allah. Indeed, Allah has appointed the Angel of Death to take the souls, except for the martyrs of the sea, for Allah Himself takes their souls. All the sins of the martyrs of the land are forgiven except debt, while all the sins of the martyrs of the sea, and their debt too, are forgiven."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7685