I hadn't watched this film for about 15 years, but after watching it again I must say that it works quite well. There is an excellent sense of atmosphere created, and Cameron Mitchell underplays his part more in the manner of a Karloff than of a Lugosi (as this is really an update of the old "mad doctor" films of the 30s and 40s). We take six diverse people--an unhappy married couple with a younger wife, a scientist, an older eccentric lady who is voiced in a Fran Drescher manner, a heroic young man (George Martin), and a desirable young woman for him to be interested in--who choose to vacation at the estate of a Count who is engaged in odd scientific research, and watch them deal with the gradual sense of doom...and the gradually more aggressive killer plants developed by Cameron Mitchell. The film is well-paced, and it leads to an exciting climax. MANEATER OF HYDRA/ISLAND OF THE DOOMED must have looked great on a massive drive-in screen back in 1967--it's still worth seeing today for the fan of 60's Euro-horror and for fans of the great Cameron Mitchell (although Mitchell does not dub his own voice).