Eamon Thomas Hennedy’s review published on Letterboxd:
After the success of Goldfinger, the spy genre became a massive part of pop culture with many television series and movies attempting to ride the coattails of Cubby Broccoli and Harry Saltzman's franchise. With that in mind, they go all out with a widescreen, underwater epic that looks and sounds spectacular but which represents the weakest installment of the franchise to this point.
For a film with an against the clock narrative such as this one and the theft of nuclear weapons, the film has a slow laid back style, instead feeling as if it simply wants to enjoy James Bond at the beach than move the plot along. Whenever the action starts, the majority of it takes place underwater which means it's either really, really slow, or overcanked and sped up to the point of absurdity.
It looks spectacular and backed up by great John Barry music and Ken Adam's production design, and you can feel the palpable sense of excitement that must have greeted it in 1965, but it's also the weakest of the 60s Bond pictures, with Terence Young's direction, stylish as it is, failing to match the zippier style that Hamilton brought to Goldfinger.
The most fascinating thing about it is its production history; the rights to Ian Fleming's novel belonged to Kevin McClory which is why he gets sole producing credit here. The nature of his deal with Eon Productions meant he couldn't produce a rival Bond picture for ten years, which resulted in this film being remade as Never Say Never Again and a long series of legalities as to who owned the film rights to 007 himself. It's a fascinating story and one more interesting than the film that ended up on screen.