Revealing mistake: When Bond and Honey are made to take showers to clean them of any remaining radioactivity, they are meant to be naked. When Honey gets out of the shower a man holds a towel up for her, but if you look closely you can see that she is wearing a flesh-colored swim suit.
Revealing mistake: James Bond and his two friends are hiding underwater while Dr. No's thugs search the river with dogs. Bond had very quickly cut three hollow bamboo stalks to use to breathe underwater through the stalks. However, you can see the sections in the bamboo, so the closed stalk sections, separated by the natural divider, would not allow air to pass through. Bond hadn't cleared through the sections with a thin pole, so these would not have been usable as breathing tubes without more work.