This looks to be some type of a ferry boat, and written on the back was Hong Kong. My best guess is that the photo dates to about the 1940s to 1950s. You can just barely see the shapes of people standing by the rails, but other than that I can’t tell much about the boat.
UPDATE: Site reader Sarah says this is the Star Ferry that crosses Victoria Harbour from Hong Kong to Kowloon. Thanks, Sarah!!