Water resistance is not a underwater watch. Like you said, the first "divers" watch was made by Omega, but they only thing diver about it was the fact that it had a case that protected it from extreme pressure and temperature. It actually had to be removed from the case to be wound.

The first true underwater watch was made by Panerai in 1936. They not only made their cases water proof (note proof, not resistant), but the over sized their dials, over sized their numbers and used their luminating compound to make the watch visible in murky and dark waters.

And I had given you more then one thing Panerai has done.