I used to swim in an Olympic-sized pool with a depth of 10 feet (3m) at one end. I could hold my breath and swim down to the bottom for a minute maybe, and looking around, it was definitely a lot of water. I could feel the pressure even there.
I also went snorkeling in Hawaii once in cove that had deep areas easily over 10m. Even looking down at that depth could be disorienting and anxiety-inducing.
A hundred meters is technical SCUBA diving depth. A few hundred meters is where military subs hang out, and not much below. A kilometer is crush depth for all but the sturdiest military submarines and special deep-diving vehicles.
I grew up with a Swim Club, and our pool went to 12' deep - and just getting to the drain at the center of the deep-end hurt my ears so bad, that it was an effort.
I can pop my ears at will in Air, but underwater, at 12' the pain is intense, and I cant normalize. I couldnt imagine say, 30' deep or anything more.
I also went snorkeling in Hawaii once in cove that had deep areas easily over 10m. Even looking down at that depth could be disorienting and anxiety-inducing.
A hundred meters is technical SCUBA diving depth. A few hundred meters is where military subs hang out, and not much below. A kilometer is crush depth for all but the sturdiest military submarines and special deep-diving vehicles.