Sayyiduna Abdullah bin Amr (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Let no one travel by sea except a fighter in Allah's cause, one performing Umrah, or one performing Hajj; let no one else travel by sea. For beneath the sea there is fire, beneath the fire there is water, and beneath that water there is fire. And the property of a Muslim in distress is not to be bought."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11078