The organisation National Historic Ships who are a wonderful resource, not least by keeping a register of historic vessels, not just salty stuff but all sorts including historic narrow boats and other inland waterways boats, are running their annual photo competition.
You can download the flyer here.
There is more information on the NHS site here.
There is also a competition for the Marsh Christian Award to a volunteer or group of volunteers who have made valuable contribution to the conservation or operation of historic vessels in the UK. More details here.