IMO, unless there is a paid captain or crew, it's clearly the owner's (shirked) responsibility. There should be no leakage into the water from an otherwise dry cable in new condition that is dipping in the water . But that cable appears to have a lot of mileage on it, possibly including a whole lot of runs pulled through the managing devices of a Glendinning cable system. . And perhaps on a rainy windy day there could be a path from dock pedestal to water ground on wet cable and connectors .....?
I would not want to have to work under my boat in the vicinity of that boat. I've been in the (salt)water and felt the onset of "minor" but quite disturbing AC muscle tingle where it turned out a dock neighbor's compromised cable was dipping. Not fun feeling and difficult to guess which way could add danger . Glad I wasn't in fresh water.