Fresh Water Mussels
I have seen piles of mussel shells left along the banks and undercuts by the 'coons.  So, I know the mussels are there close enough to shore the critters can get too 'em without drownin'. As a source of protein, mussels will do when you don't have weapons to bring down somethin' really tasty.  So, I figured I'd tie-up the dugout and see if I was as smart as a 'coon about gettin' me some meat.
The mud or sand on the bottom has to be deep enough for the mussels to bury themselves into.  So I waded out to where the bottom of the lake got squishy.  It was firm clay near the shore.  I found mud up to my ankles when I was about knee-deep in water.  It was about mid morning, and I felt around in the mud with my feet.  When I found something solid but movable in the mud, I reached down to see what it was.  I found old shells, a bone, and within about 20 minutes, eight good-sized mussels.  It was plenty for a good lunch.
The shells were striated hues of green, brown and blue.  I laid my Green River Belt Knife among 'em so you'd have an idea of scale.  The smallest of 'em reached nearly across my palm.

If a mussel is alive, it will clamp tight shut.  If it 'aint shut tight, it's dead.  Toss it!  Mussels get toxic quick after their dead.

I needed to find a place to start a fire and get them babies cooked.
A Blue Heron was near a beaver slide I wanted to put into.  I didn't want to be squattin' in the weeds tryin' to start a fire.  I wanted a path that was beaten down.
The Heron was willin' to move.
I collected individual leaves of dried grass from among the green.  Two dead-standing bushes and a log provided my firewood.
I made an oven from the burning underbelly of the log and live coals.  The mussels stewed themselves in their own juice.  They go into the coals tight shut, and begin to open as they cook.

The mussels are goin' to taste like the water smells.  I may have eaten worse things, but I don't remember what that might have been.

Chopped up and stewed, they were much better, but
that was later.  If I were goin' to survive off fresh water mussels, they would have to be smoked over the fire after they were cooked, to help cover up the mud taste.  Some wild garlic to rub 'em down with would have helped too.  By themselves, they would help you survive, but if you are like me, you'd have to be pretty hungry to make 'em taste good!