Blew $340 on a "dive ready" watch that flooded at 40 feet

I bought one of those fancy dive watches everyone on the crew kept going on about, paid $340 for it because the guy at the shop swore it was rated to 300 meters and built for working divers. First real job after that, a pipeline inspection in 38 feet of murky water down near the harbor, and by the time I surfaced the crystal was fogged and water was sitting behind the glass. Took it back and the shop told me the warranty doesn't cover "operational use," which apparently means actually diving with it. I've been using a $60 beater with a rubber strap for years and it has never once let me down. Turns out depth ratings on paper mean nothing when the seals are cheap and the crown gets bumped on a ladder. So save your money and put it toward a backup light or a better knife instead. What's the one piece of gear you regret dropping real cash on?