Well, it's ok I suppose if it's your own dog! We have a small dog and she's very well behaved. We arrived at our boat today and a mobo moored close by had a huge dog on board. It looked like a St. Bernard crossed with a Great Dane.
I was down below and our dog was on deck when suddenly I heard something thundering along the pontoon and the huge dog had jumped ship and was looking for trouble. The dog spotted our dog and came onboard our boat without any hesitation. Luckily my dog has a lovely nature and didn't growl or bark or anything. I was a bit scared to be honest, because their dog was huge. The owner came to look for it and told me not to worry because his dog was as soft as anything, the only thing was he didn't seem to have any control over it. I was a bit annoyed TBH.