Since the invention of the motion picture, several hundred films have been made that involve one or more character sinking in quicksand. A variety of materials have been used to make movie quicksand, including genuine deep mud, and performers have employed a variety of techniques to portrey being "sucked down into the depths of the mire." This article is a brief summary and analysis of those techniques.It is primarily based, admittedly, on studious observation of existing films and not on personal experience, although some off-camera experimentation has been performed. Additional comments and/or corrrections of fact are welcome and will be added as postscripts, if and when received.
The Duck-Under
In several videos produced by WAVE Productions, the last submbergence in MudPuddle Visual's "Serial Sinker" and other videos, the performers employ what may be referred to as the "duck-under technique. Starting from a position of submergence roughly to the neck (the chin in Serial Sinker) and with the head pretty much in a vertical position, the performer submerges somewhat suddenly. The maneuver may be executed by flexion of the knees (squatting) or, possibly, by an upward lift of the arms.The head may be tilted back slightly, as in "Serial Sinker" but generally not nearly as far as with other techniques.
The chief problem with this technique seems to be that the speed of submergence appears to be necessarily faster than with other methods. This appears to be because speed of movement is the only practical way to deal with the problem of excessive buoyancy. In other words, the performer must duck-under quickly or buoyancy will result in bobbing back to the surface before submergence is completed. This problem might, of course, be overcome through the use of some sort of anchoring device below the surface or through the use of something like swimmer's hand paddles to increase the force generated by an upward movement of the arms.
In all of the fils in which the duck-under appears to be used, a relatively thin, though not necessarily watery mud mixture is used. Certainly all of the WAVE Productions scenes use a relatively thin mixture of what appears to be peat and water. The MudPuddle Visuals film mentioned above uses a clay mixture but one that is fairly thin (though much thicker than the WAVE peat mixtures). Careful observation of these videos strongly suggests that the duck-under may be substantially more difficult or impossible in a thicker mixture.
The Layback
Mina Lee and Brinke Stevens in "The Jewel of Doom," Mina Lee again in "Don't Go There," and Kristine in both "Explorer Revisited," and "Young Lady, Deep Mud," all employ what may be labelled as the "Layback" technique. Here the performer assumes a semi-reclining position with the mud mixture covering the chest and shoulders. The arms are always submerged. The illusion to the viewer is that the character is in a vertical position and has sunk to the neck or chin. The submergence is then accomplished by extending the arms to the sides or overhead (but beneath the surface) and pressing upward against the mud. Some very slow submersions are possible with this method (the slowest being in Explorer Revisited and Young Lady, Deep Mud) although sometimes the very final downward movement is faster than the preceeding movements.
The layback technique appears to be the only practical method of total submergence in very thick mud, as is the case in both of Kristine's films to date. It appears to permit submergence in spite of the high level of buoyancy provided by such mud because the performer does not actually lower the center of gravity any further than the point reached when in the semi-reclining position with the head entirely above the surface. Instead, the performer rotates the body around its center of buoyancy. In other words, the added buoyancy produced as the head submerges is balanced by the upward movement of the lower part of the body and/or the arms. One can observe this in the Brinke Stevens episode as an upward movement of the mud in front of her as her face is covered. This is produced by the performer's torso rising through the mud.
The layback can produce a much more convincing submergence than the duck-under. The submergence is often slower and the face-up position is consistent with common expectations of what a person would do if being drawn down into mud. However, the technique does have its shortcomings. First, the arms are not free to contribute to the illusion of struggle. They are needed to accomplish the submbergence. This creates an inconsistency that affects the suspension of disbelief unless the thcikness of the mud or some element of the story explains why the arms are not used to struggle. In all of the above videos, it is left to the viewer to explain why the arms are not used - presumably to assume that the mud is so thick the character cannot extract the arms from it. This is a fairly easy assumption in "Explorer Revisited" and "Young Lady, Deep Mud" as the mud is very thick, but is a harder leap of faith in "Jewel of Doom" where the mud is thinner. A second proble is a subtle one relating to the set-up preceeding the layback submergence. It involves the performer initiating the transition to the semi-reclining position slightly prematurely. This results in the viewer being able to see the performers chest above the surface, revealing the semi-reclining position.This destroys the illusion that the head is tilted back as a last resort.
The Vertical Arm-Lift
A person immersed to the neck in deep water and wanting to submerge would do so by keeping the legs together and straight while lifting upward to the sides with the arms. This works well in water to produce a submergence of any desired speed. In a fluid with substantially higher density than water, however, a single upward stroke with the arms is likely to be inadequate to produce enough force to overcome the increased buoyancy unless the head is already mostly submerged. If the fluid is particularly dense this is almost a certainty. If it is less dense, but also very fluid, the performer is likely to bob back to the surface before submergence is completed. The vertical arm-lift also shares the submerged arms problem of the layback technique. The writer knows of no video example that is clearly of this technique. However, with exactly the right balance of viscosity and density - possible only in an artificial mud mixture - this technique might be capable of producing a submergence even slower and more controlled than those produced via the layback technique.
The Anchored Squat or Arm-Lift
One way to overcome the problem of buoyancy is to use some sort of anchoring device as an aid to performing a duck-under or vertical arm-lift. Such things as a pole held down by someone on the surface, a submerged framwork, a sunken anchor with a foot stirrup, any other sort of anchor might be used. One apparent example of this is the Mina Lee episode of "Jewel of Doom" in which what appears to be a pole appears on the edge of certain scenes prior to the layback submergence. To factors seem to be limiting, however, on this method. One, of course, is the aspect of safety. The performer must have an easy means of disengaging from whatever anchoring device is used and is likely to be uncomfortable with anything other than a simple pole in any case. The other relates to the point of attachment of the performer to the anchoring device. If this point of attachment is not directly above or below the performer's center of bouyancy it will cause the performer to tend to rotate in position. This may be desirable in a few filming situations if it is desired to show the character as disoriented or out of control, but in most cases will be more a problem to filming a scene than an asset. If the point of attachment is above the performer, of course, it is likely to be within the view of the camera - not a desirable situation.
The one type of anchoring device that would seem to be most useful would be a submerged anchor that the performer could grasp by means of a foot stirrup. This would be easy to disengage from and the point of attachment would be correct, though out of camera view. The performer could then do a controlled submergence by squatting. If the anchor is located deep enough so the performer is immersed to the neck prior to beginning the squat, the legs should be able to generate enough force to submerge very slowly and with the arms free to pretend to struggle against submergence. This ought to significantly contribute to the illusion of reality.The writer knows of no filmed example of this technique.
The Push Down
One way to overcome the problem of natural buoyancy in a movie quicksand scene is to use a story line that provides some external force that pushes the victim beneath the surface. The easiest device for this is probably to use another character, as in the submergence of Synda in "Jewel of Doom," or two characters in "Serial Sinker." One might use a fallen branch, an entrapping vehicle, or even a falling second victim.
Use of Negative Buoyancy
All of the above techniques require the performer to somehow simulate being pulled or sinking below the surface. Mud, in all natural cases and most artificial ones is substantially denser than water so the performer must somehow fake sinking into it. In just the right circumstances, it might be possible to perform a genuine sinking, perhaps even one in which the performer sinks in spite of genuine (or partially genuine) struggles to stay afloat. If this could be done it ought to produce a very realistic-looking movie scene. There are essentially two ways in which this might be done.
One possibility is to increase the density of the performer. This can be done through use of added weights, such as by using a skin diver's weight belt. There is obviously a safety issue here. One would not want to attempt such a stunt in mud of unknown depth. However, in an artificial mud pit known absolutely to be of slightly less depth than the performer's height, it may be deemed safe. All the performer need to to regain the surface is stand up. To stage a submergence the performer need only raise the legs off the bottom. If there is enough weight worn the performer can genuinely struggle to float and still be pulled below the surface.
The second possibility is to add some kind of low density material to the mud mixture so as to lower its density. Such materials as chopped cork or even chopped styrofoam particles may work well for this, provided their presence is not apparent to the viewer. The writer has experimented, for example, with styrofoam peanuts. These tend to float to the surface far too readily in very wet mud mixtures but will remain submerged in thicker mud. In a five foot deep mixture of sodium bentonite clay, mixed dry enough so that depressions of several inches can be made by pressing down and then releasing the surface, enough styrofoam can be added to the top two or three feeet to permit a genuine sinking. A thin layer of aome other material on the surface might be used to conceal the syrofoam pieces so the camera cannot see them.