First, the introduction. (Apologies, but it's important and relevant.) *Note: The fact that the diver is breating compressed air has a profound affect on the body if decompression standards are not met when coming to the surface having spent time at depth. Divers who do not decompress properly can (and have!) died as a result. *Note: The breathing of "regular" compressed gas (air) at "great" depths will increase what is called the partial pressure of the gasses breathed to the point where nitrogen narcosis (the "rapture of the deep") can set in. It will intoxicate and disorient a diver who "goes deep" to the point the he may end up drowning because his cognitive faculties have been compromised and he "spaces out" down there. *Note: The failure of a diver to "equalize" the pressure across his eardrums while descending can result in the rupture of the eardrum(s) and can destroy a diver's hearing in one or both sides. The issues cited are serious. Very much so. They can be life or death. But the wonderful thing is that they are very manageable. The well-developed training and the superior equipment used by divers today make the sport quite safe. The diver controls "99%" of the risk. It's an activity that is doable by most individuals. Most of us risk our lives every day in motor vehicles and we do so without much thought. We have done a personal cost/benefit ratio and have decided to risk getting in the car. We have mastered the basic driving skills and we venture forth having had a little (or a lot) of practice. No problem. That said, let us (finally!) address the question. Other than the issue of decompression, the issue of using "standard" compressed air (as opposed to mixed gas) at "excessive" depths, and the issue of equalization, the body is unaffected on the whole by the compression of the water. Get a balloon and fill it with water to make a water balloon. Be sure to get all the air out. Take the water balloon and put it in a bucket of water and hold it on the bottom. Does it get smaller? No. It is almost completely incompressible. Except for the inside of the lungs (and the interconnection between the airways and the inner ear), the body is the same way. The materials out of which the body is made, and the fact that much of it is water, make it "incompressible" with the exceptions noted. When using air to Scuba dive, air taken into the lungs is taken in at "increased" pressure because of the action of the regulator. The increased air pressure will insure that the lungs cannot "collapse" due to the pressure of the water. The lungs and inner ear aside, the body is largely unaffected by water pressure. The diver breathes normally and suffers no ill effects (with the exceptions noted). Some feel for what it is like can be had by going to the bottom of a swimming pool. In the shallows, an individual submerging will feel weightless because buoyancy works against gravity in water. In a "regular" pool, the diver may have to equalize a bit to get on the bottom, but once there, the body is not "crushed" by the water. The lungs are a bit compressed, but that is all. The diver does not notice. The pressure of the water is a factor that is "transparent" in the experience. It goes by will little heed paid to it. (It is water's resistance to the diver's movement which gets all the attention. It is a surreal experience to anyone diving for the first time - as well as returning veterans - to get in the water and become one with the element and its denizens. If an opportunity to dive presents itself, particularly to someone who had not done it, it is a chance to be jumped at. There is nothing like it anywhere. Nothing.
At 99 feet below the surface, the total pressure on a diver can be calculated using the formula: total pressure = atmospheric pressure + (depth in feet × 0.433 psi/ft). The atmospheric pressure at sea level is approximately 14.7 psi. Thus, the total pressure at 99 feet is about 14.7 psi + (99 ft × 0.433 psi/ft) = approximately 14.7 psi + 42.8 psi = 57.5 psi. Therefore, the total pressure on a diver at that depth is approximately 57.5 psi.
Air pressure (at sea level) is about 1 bar; every 10 meters below the water surface, pressure increases by about 1 bar - that gives a total of 1 + 0.4 = 1.4 bar. (1 bar is about 1 atmosphere.)
When you squeeze the sides of the bottle, you increase the pressure inside, causing the water level to rise and displacing the air in the diver. This added pressure compresses the air inside the diver, making it denser than the surrounding water. As a result, the diver becomes negatively buoyant and sinks. Once you release the pressure, the air expands, and the diver rises again.
In a Cartesian diver, the air behaves as it does due to the principles of buoyancy and pressure. When the container is squeezed, the water pressure increases, compressing the air inside the diver. This increased pressure reduces the volume of air, making the diver denser than the surrounding water, causing it to sink. Releasing the pressure allows the air to expand, decreasing the diver's density, and making it buoyant again, allowing it to rise.
Changes inside the diver, such as changes in buoyancy or density, can affect the diver's position in the surrounding fluid by causing the diver to either sink or float. For example, if the diver becomes less dense than the fluid, they will float to the surface. Similarly, if the diver becomes denser than the fluid, they will sink to the bottom.
Pascal's principle states that when pressure is applied to a confined fluid, it is transmitted equally in all directions. In the Cartesian diver toy, squeezing the bottle increases the pressure inside, causing the diver to sink as the higher pressure compresses the air in the diver. Releasing the pressure allows the air to expand, making the diver float back to the surface.
Implants do not affect the ability of a diver to descend deep.
The cartesian diver sinks because the diver wants to get to a place of low pressure
The pressure exerted on a diver 10 m underwater is approximately 2 atmospheres or 1.8 times the atmospheric pressure at the surface. This means the pressure is effectively doubled at this depth.
Pascal's principle states that a change in pressure at any point in an enclosed fluid is transmitted undiminished to all points in the fluid. This principle helps explain the behavior of the Cartesian diver, as the change in pressure when the diver is squeezed causes the enclosed air to compress and the diver to sink, and when pressure is released, the compressed air expands, causing the diver to rise.
Pascal's principle states that a change in pressure at any point in an enclosed fluid is transmitted equally to all points in the fluid. In the case of a Cartesian diver, when you apply pressure to the container, the pressure is transmitted to the fluid inside, causing the diver to compress and sink. When you release the pressure, the diver expands and rises due to the equal distribution of pressure in the fluid, demonstrating Pascal's principle in action.
Assuming that by 'amateur diver' you mean a recreational diver without any professional qualificaitions, the recommended limit as determined by PADI (Professional Association of Diving Instructors) is 18m (60ft) for an Open Water diver, 30m (100ft) for Advanced Open Water and 40m (120ft) for a Divemaster. BSAC (British Sub Aqua club) sets the limits as 20m (67ft) for an Ocean Diver, 30m (100ft) for Sports Diver and 50m (165ft) for Master Diver. So in answer to your question, no, you couldn't 'swim where the water pressure is more than 65 ps' unless you were a technical diver or a BSAC qualified diver, as at 165ft the pressure is around 69ps.