Submarines are not glued tight, yet they are waterproof.
Much bigger deal for Apple is design. Exposed screws sealing the back cover would give Jony Ive OCD ticks, I'm sure
Much bigger deal for Apple is design. Exposed screws sealing the back cover would give Jony Ive OCD ticks, I'm sure
Submarines are glued tight; all the body panels are welded together. They do this because making waterproof riveted joints is hard [0]. Riveted joints would flex and open up, requiring constant maintenance and caulking, and early riveted subs would leak trails of fuel behind them (and significantly into the sub itself!)
Second, submarines aren't even waterproof. There's lots of things that are hard to seal, like the spinning propeller shaft. Submarines have a natural advantage over your phone in this regard: all the water that leaks in can be pumped out.
Under the new regulations, phones can't be glued or welded shut, and there's not much room for a bilge pump in the average modern smartphone.
[0]: https://www.subsim.com/radioroom/showthread.php?p=1518898