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 other than a fighter, a pilgrim performing Hajj, or one performing Umrah travel by sea, for beneath the sea there is fire and beneath the fire there is sea." And he said: "A ruler should not buy anything from one who is in distress and hardship."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11079