The National Oceanographic Museum of Vietnam sits at the southern end of Nha Trang beach and contains an extensive collection of marine life — preserved specimens, shells, corals, and live fish and sea creatures in an aquarium section. The building is a French colonial structure from the 1920s, and the older exhibition halls have a pleasantly dusty, old-fashioned character that contrasts with the slicker aquarium section added more recently.
The live aquarium tank section is the main draw, with a variety of tropical fish, sea turtles, and rays. The preserved specimen collection is extensive and scientifically interesting if you have any interest in marine biology. Admission is cheap; allow about an hour.