Originally Posted by mm43
As has previously been said, there will be no rush to the bottom, as increasing pressure equals increasing surface friction.
Generally agreed with your post, except this statement. Perhaps you meant something else. The density of water changes very little (some, but not much) with increasing pressure. The form-drag (in the applicable regime) is proportional to the density of the media, and no other property of it. Thus drag is not a significant function of depth.
Edit: mm43 did mention skin drag in his post, and I believe that involves the viscosity of the media. I found a reference (
Water Viscosity at High Pressure and Temperature) that shows the viscosity to double at 1Gpa, roughly equivalent to 4000m depth. However, I think the drag of these A/C parts is dominated by form drag. I'm definitely getting out of my area here, but I've never heard the MEs I've worked with factor depth into drag calculations.
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I might point out that objects that tend to "kite" off the vertical during descent will also be likely to turn. Thus most objects will still end up near each other after either a straight or spiral descent. The example of the Ark Royal differs in that symmetry and mass will make the turn rate very slow, and thus a hull section could wind up a long way away. It is the rare object that will drift away on a constant heading.