GAIA GPS gets my vote. Pre-trip download your marine chart or topo map of the area you’ll be paddling in. Record your trip after putting your device in airplane mode. Supports android and IOS devices.
MCImes, that’s one of the “must have”
A good paper or plastic M-app plus analog, magnetic compass are good to have, regardless what electronics you bring.
For tracking speed, distance, and similar data, I use the same device Rookie mentioned, the Garmin 310XT but don’t bother with connecting to a computer. I just delete the histories frequently, after looking at them.
Several months ago I bought a handheld dedicated GPS unit. I liked it except for one critical feature: the plastic latch for opening up the backside had already been broken off. It also had a few oddly out-of-region businesses “someone else” had entered in. I figured the store had sold me—at full price and presented as new—a returned item. Drove the 75 miles back to the store, asked the person at service desk, and she took one look at a black marker slash on the side of box. Told me the sales rep should NOT have sold it to me as new. The slash mark was the store’s way of denoting returns.
I won’t be buying from that guy again, and I have not replaced the unit, just got a refund. The store had no new ones. Also, the plastic latch tab was so tiny I could easily see how it would have been broken.
In my research into the Apple watch (5), I came across an app called Workoutdoors which is getting rave reviews. It’s also for the iPhone, iPad and iPod Touch. Something you might want to check out to see if it meets your needs. http://www.workoutdoors.net/
@CA139 Your genuine concern shows, and is appreciated. People don’t always think about the “what if” situation, and then aren’t prepared when the “what if” happens.