Dr. John Lilly: In the tank, the following stages have been experienced:

(1) For about the first three-quarters of an hour, the day’s residues are predominant. One is aware of the surroundings, recent problems, etc.

(2) Gradually, one begins to relax and more or less enjoy the experience. The feeling of being isolated in space and having nothing to do is restful and relaxing at this stage.

(3) But slowly, during the next hour, a tension develops which can be called a “stimulus-action” hunger; hidden methods of self-stimulation develop: twitching muscles, slows wimming movements (which cause sensations as the water flows by the skin), stroking one finger with another, etc. If one can inhibit such maneuvers long enough, intense satisfaction is derived from later self-stimulations.

(4) If inhibition can win out, the tension may ultimately develop to the point of forcing the subject to leave the tank.

(5) Meanwhile, the attention is drawn powerfully to any residual stimulus: the mask, the suspension, each come in for their share of concentration. Such residual stimuli become the whole content of consciousness to an almost unbearable degree.

(6) If this stage is passed without leaving the tank, one notices that one’s thoughts have shifted from a directed type of thinking about problems to reveries and fantasies of a highly personal and emotionally charged nature. These are too personal to relate publicly, and probably vary greatly from subject to subject. The individual reactions to such fantasy material also probably varies considerably, from complete suppression to relaxing and enjoying them.

(7) If the tension and the fantasies are withstood, one may experience the furthest stage which we have yet explored: projection of visual imagery. I have seen this once, after a two-and-one-half hour period. The black curtain in front of the eyes (such as one “sees” in a dark room with eyes closed) gradually opens out into a three-dimensional dark, empty space in front of the body. This phenomenon captures one’s interest immediately, and one waits to find out what comes next. Gradually forms of the type sometimes seen in hypnogogic states appear. In this case they were small, strangely shared objects with selfluminous borders. A tunnel whose inside “space” seemed to be emitting a blue light then appeared straight ahead. About this time this experiment was terminated by a leakage of water into the mask through a faulty connector to the inspiratory tube

In our experiments, we notice that after immersion the day apparently is started over, i.e. the subject feels as if he has just arisen from bed afresh, this effect persists, and the subject finds he is out of step with the clock for the rest of that day. He also has to readjust to social intercourse in subtle ways. The night of the day of the exposure he finds that his bed exerts great pressure against his body. No bed is as comfortable as floating in water.