So that's definitely not an easy answer, and why I despise the way most manufactures rate the water resistancy of their watches. They say it's water resistant to 100m, but then say you shouldn't scuba dive with it, only submerge the watch (like swimming). IMO they should all rate the watch for the rating a normal person will exert on the watch at that depth. Like you said, someone thrashing about at 50' puts more pressure on a watch than if it was attached to a fishing pole & just 'dropped' to that depth with no movement, which is how most manufactures rate the watch. It's ridiculous because I don't know of 1 person who doesn't move their arms once they're in the water. Granted it's not an exact number, but they can certainly come up with a better, more accurate rating. However, were they to do that their 'resistancy' on the dial would be less & the watch would be perceived as less of a diver. So, they've developed a model that shows the maximum number for marketing, when in fact it's not accurate.
Now, that all said, the Rolex manual states the watch is waterproof to the depth rated on the watch. And each Rolex is tested in 2 separate tests (one dry & one wet) to 90% of it's rated depth rating. So I'd have no problem taking a 300m Rolex to 250 m (not that I'd ever go that deep) where I certainly wouldn't do that with many of my others.
Regarding the why 12,00 ft. rating is needed for the DS, I can't answer that one...
Now, that all said, the Rolex manual states the watch is waterproof to the depth rated on the watch. And each Rolex is tested in 2 separate tests (one dry & one wet) to 90% of it's rated depth rating. So I'd have no problem taking a 300m Rolex to 250 m (not that I'd ever go that deep) where I certainly wouldn't do that with many of my others.
Regarding the why 12,00 ft. rating is needed for the DS, I can't answer that one...