GPS

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I've used hand held for longer then I can remember.

Your questions really depends on usage. We can assume you mean lakes. In that case a basic unit this is easy to use will get you to any lat/log within 10 feet but you need paper charts or map chips or Google for the lat/log. The GPS is just that, Global Position, not Global Mapping.  If you want maps that's not GPS per say. Some GPS map, some do not. I have an old GPS that is still accurate and easy to use but it gives me a navigation to a point. So I know I'm 8000 feet away from my target and it's bearing is 210 degrees. It doesn't know the Grand Canyon is in the way.

Like most things, it's not as simple as asking "what do I buy?"

--Do you need maps and if so how accurate and how much do you want to load and unload and update them?
--Do you need color display? (easier to see)
--How big of a screen do you want? Boating you want BIG, Hiking/paddling you want SMALL. Car (SatNav) is medium.
--How easy is it to use? Can you use it with one hand while steering the boat? Can you operate it with gloves on?
--Water proof? How much? 3 meters? (you'd think they would all be but they are not, Garmin told me, a waterproof bag is better and cheaper so they don't waterproof ever model) Water resistant to mist and rain is common.
--Battery life? Most of mine will not make 8 hours so I have to turn them off for long crossings or trail heads to conserve batteries. (I like navigating with paper charts so this doesn't bother me to check every few hours with the GPS and then turn it off)

Lastly, if you don't have a lat/log or waypoint you want to go to, don't expect much. Sure they tell you your at 94 50.45W but were is that? Your maps will not tell you about every hazard to navigation so your still going to need the skills you got in cub scouts.

A gps saved me from spending a long cold night in the woods when I lost a trail on a solo day hike. I was miles from help and lost. I had a waypoint from the day before otherwise I may have been no more.