This is meant as a replica of a 16th Century Sultan Bolkiah Mahligai Barge. This ceremonial barge was completed in 1967 to mark the 1,400 anniversary of Nuzul Al-Quran, which is a holiday commemorating the day when the words of the Quran were first revealed to the Prophet Muhammad.
All in all, there's no question that the mosque and its royal barge are quite beautiful. Clearly no expense was spared in its design and construction.
Royal barge at the Sultan Omar Ali Saifuddin Mosque.