All anecdotal but I regularly swim laps (a few times a week), shower, and free dive with my Series 4.

Just last week jumped off a 30 foot cliff and the clasp came loose, it literally flew off my wrist and sunk to the bottom of the ocean. A friend helped me retrieve it, maybe 30-40 feet down. Perfect working order as of today!

I once did get some sand in the crown and needed to wash it out thoroughly but no other hardware problems in the 3 years I've owned it.