Last updated: July 16, 2026

Quick Summary: Bioluminescent plankton glow in the water when disturbed by a paddle or a passing fish, and Lan Ha Bay near Cat Ba is one of the best places in northern Vietnam to see it on a night kayak. Sightings are most likely on dark, moonless nights, and never guaranteed.

Here is the thing almost no one will tell you . The three bays are located on the same sea area, on the same drowned limestone islands and islets, and they look the same. If we showed you three photos with the labels removed, you could not tell which bay is which, and neither could we. So the real question is not which bay is prettier. In this Halong Bay vs Lan Ha Bay and Bai Tu Long comparison, Beka Travel shares what actually changes your day on the water, based on the trips we run out of Cat Ba every week.