Factual error: The manner in which "Hamby" fell into the hole (or well) did not reflect physics or reality. He was running/chasing Joey and Matt. Whenever one walks or runs, one's feet are never straight down together (like standing), so only one foot could have been over the hole or failed to clear it. Hamby should have tripped and fallen over (face forward) with his upper body landing past the hole. This should have kept him from falling straight down into the hole (as if dropped from above the hole).
Factual error: During one scene, a police siren can be heard in the background. However, this was 1960/1 and police sirens were not introduced into the UK until 1963. Before that, police cars had bells.
Factual error: After Maya Peters is brought into the recompression chamber because of an injury, the timer is shown counting down by hundredths of a second and skips from 1 to 0 without showing 0.99-0.01. (01:24:30)