Marker buoys vs GPS or both
We used to use floating lights pre-GPS to mark reefs for trolling at night. Actually had the Coast Guard come flying out one night thinking there was a problem....and in their haste they just about swamped us. So they almost had a rescue on their hands.
I anchor up in the area of my target with the Minnkota Spot-lock, then cast the T-pod out and drag it back, while observing my iPhone display for the target.
Disadvantage is that it is slow, and the Wifi connection gets lost if you reel too quick. Advantage is you drop no markers, and there is less doubt if you are exactly where you want to be.
Also works well when you anchor off steep-breaking structures, and want to fish a particular depth, but don't want to be 25' down over 35' of water....
Still carry the markers, but only drop them if I am the only boat anywhere.
I still use bouys but made my own. The orange, yellow, pink, or whatever color ones you get at a retailer draw attention. "Hey! There's a bouy over there! Let's fish that when he leaves!" Nope, I don't play that game. I cut the string off of those and tied it on empty gatorade bottles or soda bottles. If someone sees something like that floating they won't think it's marking a spot. They'll think some jerk tossed trash overboard so they never think twice about it.
Just stirring the pot!