This
could be The Lost Continent (1968), 'cept for the tenticle bit. In this movie, a guy's hand gets mauled by killer sea weed. Also, the ship(s) and islands aren't haunted, but, well, it's a long, weird story.
For more info to see if it matches what you may be remembering, see review at StompTokyo.
http://www.stomptokyo.com/movies/l/lost-continent.htmlregards,
Apostic