A lake shaped by karst and sea
The appeal begins with the view into the water: forest frames a lake whose clarity can make the bottom and reflections seem unusually close. The provincial government describes an upper layer supplied by freshwater from the surrounding karst and a lower layer influenced by seawater. That combination explains the local description of a lake with “two tastes”; it is not an invitation to drink the water.
In July 2026, government geologists and tourism officials assessed Labuan Cermin within the Sangkulirang–Mangkalihat geopark programme. An assessment is distinct from a completed designation. Visit for the landscape and its local story without assuming that it carries a particular international accreditation.
Plan through Biduk-Biduk
Biduk-Biduk is the immediate planning base. Official Berau material describes the final approach by local boat from the Labuan Kelambu jetty area. Agree the actual departure point with the lake management, together with the return arrangement and equipment available on your date. A mainland drive and this local boat transfer need their own space in an East Kalimantan itinerary.
Do not treat the lake as a short excursion included in a Derawan or Maratua island stay. Those are different routes, with different departure points. Allow roughly half a day for an unhurried lake outing once you are based locally; the longer journey to Biduk-Biduk is additional. This is a planning suggestion, not a scheduled tour.
Follow current lake rules
Government reporting confirms managed visitor use and facilities, but it does not guarantee the same opening hours or water activities every day. Check current admission, boat arrangements, life jackets and any restrictions before travelling. Ask whether advance booking is needed for your group, especially around holidays.
Clear water does not establish safe depth or safe swimming conditions. Enter the water only where the management currently permits it and follow instructions from the boat crew. Keep food and litter out of the lake, avoid disturbing the banks and do not remove aquatic life. A quiet shore or boat visit is worthwhile even when swimming is unavailable.
Keep the coastal day flexible
Combine the lake with time around Biduk-Biduk rather than stacking several distant Berau attractions into one day. Confirm your overnight base and onward transport before committing to an early departure. Weather, local operating decisions and the condition of the approach can change the shape of the day; leave enough time for the return journey.
