A sinus squeeze results when, while descending, you are unable to equalize the pressure between the outside and the inside of your sinuses. This is incredibly painful and will cause you to immediately abort the dive and return to the surface. It sucks, but you’ll bail out before any actual harm is done. Inability to clear your ears is the same basic principle, but with your middle ear rather than your sinuses. It hurts like hell, but unless you’re a complete idiot you’ll abort the dive before rupturing your eardrums. What can be fatal is a reverse sinus squeeze. Same idea as a regular sinus squeeze, except that by some flavor of awful luck you were able to equalize your sinuses on the way down. So now you’re at 90 feet, you’re close to your no decompression limits, and it’s time to come back to the surface. Except you ascend five or ten feet, and your sinuses don’t equalize. This, my soon to be late friend, is a reverse squeeze. If you ascend, you risk kinda sorta exploding your head from the trapped pressure. If you don’t ascend now, you’ll either run out of air and drown or die from the bends when you do eventually resurface. You, soon-to-be-late friend, are absolutely screwed. So why not just load up on Sudafed and jump in? Couple reasons. First off, it’ll make you a little fuzzy in the head. That will be compounded by some level of nitrogen narcosis which can make you downright stupid. Not a good idea. Second, nobody knows for sure just how the stuff works under pressure. And finally, how do you know when it’s going to wear off? In fact taking a decongestant before diving is almost a sure fire way to give yourself a reverse squeeze. The primary benefit of dive bombing was precision compared to level bombing at high altitude. Bombs are heavily influenced by their aerodynamic designs and the conditions of the air along their path. With the technology of the 1930’s and 1940’s, it was very hard to predict this with an aircraft of this era, as price flight path is critical in free fall bombing.
However, dive bombing eliminates much of the horizontal element of a bomb’s flight. All the pilot had to do was locate the target and dive at it. This enabled a pilot to hit a small target like a tank or a cruiser. Contemporary level bombers were incapable of such accuracy. With modern bombs, GPS or laser designation is used to change the path of the bomb in flight with small fins, as well as better direct aircraft at high altitude. Thus, it’s primary purpose is null. Then come the problems with dive bombing. It requires going into a steep dive that puts the aircraft in range of short range AA. An F15E would not be subject to shoulder fired SAMs or autocannon fire at its usual operational height. This means an insurgent on the ground has no way to hit him without sophisticated SAMs. Diving neutralizes this advantage. It is even worse against conventional forces, as they will see the attacker flying at altitude and fire mid range SAMs, then direct short range AA like truck based anti-air, like the Russian Tunguska systems. It unnecessarily puts pilots at risk for no advantage in an era of laser guided bombs. Similarly, diving in jets increased the risk of pilot error or incapacitation, both problems with prop driven dive bombing. Controlled and uncontrolled flight into terrain are already huge killers, and they were not uncommon in the dive bombers of old. Scuba is out forget it. I’m not sure you could even breathe is such a mixture weighing on your body. No data exists for it. Even in a hard suit it would be impossible to move without servo assisted motors. I am not even sure you could design a remotely operated vehicle that was not just a chunk of lead with treads and a screw drive on it. Not sure what the purpose of diving tar is either. Visibility is zero. BY the time you did build something that could navigate tar it would be something that could navigate soil as well and you end up with a snake like vehicle pulling itself through the ground by forcing matter through it or out of the way. The very best design would probably be something like an earthworm that ingested what was in front of it and expelled it out the back mechanically.