Robert Mitchum uncredited role involves knot-tying training( at 19 minutes into the film). Sailors stand in a row tying knots on a horizontal rope stretched across. Mitchum is the tall sailor on the right. He also is the oarsman in one of two rowboats lowered over the side of the ship (at 25 minutes). He is shown in the close-up shot near the striped ball-shaped mine. His mate chops haphazardly at its tow rope until they both are blown up.
The failure of the original copyright holder to renew the film's copyright resulted in it falling into public domain, meaning that virtually anyone could duplicate and sell a VHS/DVD copy of the film. Therefore, many of the versions of this film available on the market are either severely (and usually badly) edited and/or of extremely poor quality, having been duped from second- or third-generation (or more) copies of the film.
During knot tying training, the instructor is inspecting each trainee's work. When he looks at Tennessee Smith's knot, he says "4-oh, Smith". The Navy grades on a 4.0 scale with 4.0 being outstanding.