Visible crew/equipment: During Marilyn Lovell's nightmare, the crew experiences cabin decompression. Right when the master alarm goes off, you see a piece of monofilament attached to Jim Lovell's suit hose, used to try and simulate zero G to make the hose appear to be floating. (00:13:20)
Visible crew/equipment: Right after the explosion, Lovell tells Houston that they've got multiple cautions and warnings, and they've got to restart, then Swigert says, "I'm going to SCS," and he flips the switch. In the next wideshot of the trio, we can see the arm and fingers of a hidden crew member wearing a short sleeve blue shirt, who's holding up a hose at the bottom right corner of the screen. This is only visible in the fullscreen version. (00:51:20)
Visible crew/equipment: Immediately after the accident, when Swigert is struggling to close the hatch, as he pulls the hatch away, just before he says that he can't get it to seal, a camera is briefly visible sitting in the tunnel through to the LM. (00:52:25)
Visible crew/equipment: During the moon landing daydream sequence, Lovell is shown performing the typical low-gravity moon walk. The thin wires used to facilitate the hopping effect can be seen at the top of the frame, and stand out against the light metal finish of the lunar lander. (01:13:30)
Visible crew/equipment: Just after Lovell secures the hatch for LM jettison, and Swigert states "Okay, pyro batts look good, I don't think we're gonna have to tie those other batteries," there is a visible bearded crew member wearing glasses and a hoodie on the lower right hand side of the screen. This is only visible in the fullscreen version. (02:01:00)
Answer: Spacecraft re-enter Earth's atmosphere at extremely high velocity (thousands of miles per hour). Atmospheric friction slows the spacecraft descent somewhat; but, without parachutes, the Apollo spacecraft would still reach the surface traveling at hundreds of miles per hour. Landing in water at such high speed would be like hitting concrete, which would of course be instantly fatal. Hence the necessity of multiple parachutes. The Apollo program (and all early U.S. manned space programs) chose to land in the ocean for two reasons: 1) It was easier to track spacecraft re-entry from horizon-to-horizon at sea without visual and radar obstacles, and; 2) It was faster and easier to position several Navy vessels in the general splashdown location, then deploy helicopters to rapidly retrieve the astronauts and their spacecraft.
Charles Austin Miller