Diving from a platform height of 10 meters I will enter the water at approximately 35 MPH.
The triplock and dial gaskets on my Submariner would not even notice that.
But they would feel something at a depth of 300 meters.
As for splashing your arms in water this has been put to rest so many times.
At one time Rolex stated on their website that the triplock was rated to 500 Bar with the crown unscrewed.
Looks like the crown being screwed in just prevents operation of the crown under water - don't change the date and time at 300m depth.
As confirmation of this the Daytona is rated to 100 meters but the pushers have no sealed caps on the screw locks they only have seals on the stem - the screw down function is there to prevent accidental operation under water.