This is a well-meaning but dull museum unless you're a real nautical nut. The museum's main attraction is the 1920s RCMP Arctic patrol vessel St. Roch, the first ship to find the Northwest Passage, preserved with most of its original stores and equipment onboard. Tours of the St. Roch are popular with kids -- they get to clamber around the boat poking and prodding stuff.
The other half of the museum displays model ships, maps, prints, and a number of permanent exhibits. If the weather is pleasant, walk across the front lawn at the edge of False Creek to Heritage Harbour, where the museum keeps a collection of vintage boats. You can also catch the miniferry there to Granville Island or the West End.