I'm 5' 8", only 140lbs soaking wet, and surf hunt the beaches of Florida's surfing capital. Here's some more tips....
1) A large "heavy" scoop is a big advantage. The heavier the scoop the easier it is to get into position and keep it there. I use to use aluminum scoops but they simply move to easy in the currents which makes them harder to control.
2) Time your digging effort. I do this "a lot"....sometimes forcing my scoop into the bottom but then waiting until the swells have passed before trying to retrieve the target. If I get blown off location the scoop usually stays anchored in position allowing me to easily find it again, and the anchored scoop also helps me stay in position during the passing of swells. Usually there will be a slack period between swells, that's when you make your move. This is one time when patience is a true virtue.
3) Body position....I never attempt to snatch a target with my back to the swells. Much easier to hold location when you know what you're going to be working against.
4) Above all, and as others have already suggested, master the blind scooping method on the wet sand or shallow water before you ever attempt hunting in the swells. Where I hunt the water is so disturbed you couldn't see the bottom a great deal of the time so it's vital that you can center your target and then retrieve it blind.
5) Like everything else, the more time and effort you put into it the easier it will become, However, on the average day there will still be a fair amount of targets that never come easy. Just the nature of the elements you're hunting.
6) Gold, Platinum, Silver,...such as rings, chains, bracelets, earrings,....very dense items with small surface areas so they usually don't get moved all that easily. Coins, aluminum, scrap and slaw tend to move around on you much more easily.
PS: I use the large stainless Stealth scoop. Hated it at first but love it now simply because it is heavy and easier to control in the swells.