Tafseer Ibn Kathir of AL KAHFI [61]

فَلَمَّا بَلَغَا مَجْمَعَ بَيْنِهِمَا نَسِيَا حُوتَهُمَا فَاتَّخَذَ سَبِيلَهُ فِي الْبَحْرِ سَرَبًا

But when they reached the junction between them, they forgot their fish, and it took its course into the sea, slipping away.