Oil on canvas
Metropolitan Museum of Art, New York
gcaptain has his ship photo of the week. Tugster has his Daily Ship and he points the way to Ship of the Day, and Never Sea Land has Mermaid of the day
So, at Kennebec Captain, featured above is Winslow Homer's well known painting "The Gulf Stream". This painting does not have any mermaids but it does have, not only a boat, but a man in peril, a ship, rough seas, sharks and a waterspout. You can see it full size here. Winslow Homer: Behind the Scenes Exhibition at The Art Institute of Chicago is here.
Homer was asked to provide a couple of lines to describe the painting. He answered "I regret very much that I have painted a picture that requires any description."
Others have given their interpretations however, the Wikipedia article is here with a couple of links to essays