It is not known of course how many were inside the ship as it sank, but most witnesses state a large amount of people were on the stern's decks and 3rd class main room (or maybe smoking room?) under the poop deck towards the end of the final plunge.
I would think the suction would have pulled a lot of people on those decks down during the final plunge, sometimes with enough force to tear the lifebelts from them. As for the fact that many of the bodies seen in the immediate hours after the sinking disappeared over the next few days--the currents would have carried some away pretty quickly, also some would have lost buoyancy and slipped beneath the surface as the days went by and nature ran its course. Remember, the recovery vessels could not get to the site for a couple of days.
Also, many were probably still inside the ship. I recall reading there were a few survivors who reported a great suction that almost pulled them into vents or open windows as they tried to swim away from the sinking ship; undoubtedly some less fortunate were in fact met with a fate like that. Persons sucked down with the vortex of the final plunge would have had internal pressure-related injuries and that would have of course been fatal and perhaps made them non-buoyant. In any case, a horrible fate.
It's also well to remember that the clothing of 1912, particularly women's clothing, would have worked against survival and floatation.
It was a simple matter of volume and weight; there were not yet many synthetic fibers besides rayon (called "artificial silk" until the 1920s), with wool predominating for most outer garments. Wet wool is extremely heavy, as anyone who has ever washed a sweater by hand can attest. A passenger wearing a wool suit or dress and a coat would be bearing weight that might easily have overcome the floational capacity of his or her lifebelt as soon as the wool became soaked. Also remember that woolen undergarments, in the form of "union suits" and other neck-to-ankle designs, were fairly standard for men at this time.
Women would have had it even worse with the additional layers of chemise, corset, petticoats and stockings.
P.S.: While this has nothing to do with the sinking of bodies, Titanic's passengers would also have been greatly hampered by the high-topped footwear of the day, which made flexing of the ankle - a key need when swimming - difficult. Again, women would have had it far worse than men; women's shoes of the day were very tight in the ankle area, in accordance with a then-prevalent theory that such support at the ankles kept them trim and slender.
A warmly dressed woman with a large frame might well have gone down like a rock - the combination of high body weight, wet wool weight and lack of ability to perform swimming motions decently well (assuming she even knew how) might have doomed her almost immediately.
James Cameron's movie depicted many hundreds of bodies just sitting in the ocean after the ship went down. Whether that is true or not, it could partly be correlated by survivor testimony that stated a great wail of sorts could be heard, that to some, sounded like chirping crickets, that slowly died away.
Now, with Cameron's movie in mind, and assuming that there were hundreds of bodies on the surface...it does make you wonder if Carpathia, Californian, or Mt. Temple did a through job of looking for bodies or not. Yes, there's a current in the water, but from 2:20, when most of the people would have been in the water after the ship went down, to rescue at 3:30-8:30, it just seems to me, that all those bodies would be just sitting there. Sure, it was hard to really see anything in that pitch darkness, but I think that by dawn, there would still have been a substantial amount of bodies just laying there.
Perhaps, IMHO, the cold hard truth is that the three rescue ship aforementioned, had no accommodations for dead bodies, so they sailed on, and stated that there were no bodies to be seen. Of course this couldn't be verified, because by the time other ships passed by, days had passed, and the current did its work.
"But wait!" you say, "there were 705 survivors, plus additional crew and Carpathia's own passengers"
well, the survivors and regular passengers would be too occupied with helping and sorting out what they just witnessed, and the crew certainly doesn't or won't want to admit leaving bodies behind for fear of a lawsuit.
Waterlogged clothes are heavy and a problem when trying to pull yourself or someone else out of the water (and into a lifeboat for instance), but obviously the weight of the water absorbed by clothing is irrelevant to buoyancy when you're in the water. Only the dry weight of the clothing will be added to the load, and at least in the early stages trapped air may provide extra buoyancy. Most modern survival manuals recommend that you don't strip off before taking to the water from a sinking ship, especially if wearing a lifebelt to help keep you afloat. Crucially, a couple of layers of woolen clothing can slow down heat loss by up to 75%.
Well, yes, it would be. Especially if it didn't fit in with your plans for the day. But seriously, it depends on the circumstances. If you're on a summer outing on the river and all you need do is swim ashore then a lot of clothing won't help the situation. If you're in very cold water waiting to be rescued you might be glad of them, especially if you have a lifebelt to offset the extra (dry) weight.
Sounds like you forgot about that Webley in your pocket (as one does on these occasions). I must admit, Sandy, in the light of your final sentence above I contemplated not replying - just to give you a Bruce Willis moment!
Would it have been possible for bodies to have been "picked up" by ice as they floated in the ice field? I'm thinking about the ice maiden story, in which a Russian trawler supposedly retrieved the preserved body of woman dressed in Titanic-era clothing from an ice floe. (I'm not referring to the rumor about living survivors milling about on ice in the vicinity of the Californian, and dismissed as seals.) I just wonder if, considering the movement of ice and changing water temperature in ocean currents, bodies might have actually been "scooped up" by - or even incorporated in - ice, as happens with rock and biological matter.
Improperly worn jackets, jackets grabbed on the surface at the last minute, bodies slipping out of jackets, people trying to get out of water-sogged clothing first removing their jackets. And I have to concur, many people going down without buoyancy garments, and simply having the air forced from their lungs. I'm sure a large number of passengers and crew went down inside the vessel, either trapped or avoiding the panic outside, staying warm and dry for as long as possible, praying, or resigned to death.
Even if people were wearing life vests, their efficacy would depend on how far the suction or other factors (like being indoors within the ship) pulled them down. The buoyancy provided by the life vest decreases with depth and after a certain stage it ceases to be effective.