Trepang Bay is a coastal bay on the Cobourg Peninsula within the Garig Gunak Barlu Marine Park in the Northern Territory. The bay is part of a remote marine park environment, characterized by low-lying land and exposure to open ocean conditions. The entrance to Trepang Bay features reefs, indicated by breakers off its eastern side, which create a potential surf zone and a significant hazard for paddlers entering or exiting. This area is exposed to westerly winds, offering little shelter from that direction, and is subject to strong tidal currents, which can significantly impede progress for vessels, including paddled craft. The tidal flow can run hard enough to reduce forward speed to less than a mile in twenty minutes even with mechanical assistance, indicating that paddlers must carefully plan their transit to work with the tide, not against it.

The bay holds historical significance related to Macassan trepang (sea cucumber) fishermen, who conducted seasonal forays and left behind dugout canoes, and it was also noted by early European settlement expeditions from the Victoria Settlement at Port Essington. Paddling here is a remote expedition undertaking, suitable only for experienced paddlers prepared for open water crossings, variable monsoon winds—including northwesterlies in the wet season and southeasterly trade winds—and the need for precise tidal navigation. The surrounding area is part of a protected marine park, so visitors should be aware of and comply with all park regulations regarding access and activities.