Well, this museum is mainly two ships. One, beign the Star of India is a old trading ship that now resides in the harbour. During the summer, movies are shown on the deck, and you can walk throgugh the ship. It is not uncommon to see school groups spend the night, working as if on an actual voyage. You can go below decks and into most of the cabins.
The other, is another ship (boat, more or less) that has been converted to a floating museum. It a very unique mueseum, and pretty cool. However, if you miss this, don't feel to bad.
Over all, the admission is cheap and worth it if it is your first time.