The National Civil Defense Steering Committee said the crash happened at around 8:40 a.m. on Sunday in the Van Boi area.
A wooden tourist boat operated by Nguyen Van Bay was carrying 10 passengers and one crew member when it was hit by a larger iron-hulled vessel carrying 31 passengers and traveling in the same direction.
The impact caused the smaller boat to overturn and sink, throwing all those on board into the water.
Nearby vessels quickly joined rescue forces to pull the victims from the bay, but the female tourist from Hung Yen could not be saved.
Authorities said both boats had valid inspection certificates and were licensed to operate. An investigation is underway to determine the cause of the collision.
