The Quang Ninh Inland Waterway Port Authority said it had cleared several tourist boats to depart from Halong International Cruise Port and Tuan Chau International Passenger Port shortly after services resumed.
Most of the departures were overnight cruises, as there was insufficient time for day cruises to complete sightseeing trips before returning the same day.
The National Centre for Hydro-Meteorological Forecasting said Storm Maysak weakened into a tropical depression after moving inland in China's Guangxi region before weakening further into a low-pressure area, posing no further direct threat to Vietnam.
At 1 pm, the centre of the tropical depression was located over Guangxi, with maximum sustained winds of 50-61 kph and gusts of up to 88 kph. It was moving north-northeast at about 10 kph.
The system is expected to continue moving northeast over the next 12 hours before dissipating into a low-pressure area.
Forecasters said strong winds and rough seas would persist in the northern Gulf of Tonkin and advised vessels to continue monitoring marine weather forecasts.
