ENOfficial
‘Abdallah b. ‘Amr reported God’s Messenger as saying, “Do not sail on the sea except when going to perform the hajj, or the ‘umra, or when fighting in God’s path, for under the sea there is a fire and under the fire there is a sea.” Abu Dawud transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَرْكَبِ الْبَحْرَ إِلَّا حَاجًّا أَوْ مُعْتَمِرًا أَوْ غَازِيًا فِي سَبِيلِ اللَّهِ فَإِنَّ تَحْتَ الْبَحْرِ نَارًا وَتَحْتَ النَّارِ بَحْرًا» . رَوَاهُ أَبُو دَاوُدَ
sunnah.com