Hi Wishful,
I used my wife's fitbit for a little while. I found it to be really useful. I'm a bit of a stats nerd and have been keeping track of my exercise/weight for years. The fitbit added and extra element to those stats.
I liked the way the fitbit tracks your sleep and heart rate. It is interesting to look back over the data and keep track of where you are at.
The one thing I found was that during high intensity exercise, the heart rate tracking didn't work properly, which was a bit of a bummer. Maybe it was the way I had it set up, but that is what happened to me. Others may have found differently.
I haven't used Samsung or Apple watches. But they cost a fair bit extra. So it might be worth starting with a fitbit and then if you like it, maybe look at alternatives or just stick with the fitbit.
There is a reviewer called DCRainmaker. He is one of the best reviewers out there.
https://www.dcrainmaker.com/ has no affiliations, so you can trust his reviews, it may be worth taking a look.
I reckon one thing to get if you can, is something that is waterproof. But then that costs extra. But you can wear it while you are working the river!