The pinpointer is definitely not a Garrett, so I'm not sure what brand it is right now (I'm at work.) However, I will make sure that it is waterproof first.
If your pinpointer isn't waterproof, then nope. I recommend the Garrett ProPointer AT. You'll need a hard scoop to dig into river rock (unless you're in silt only, and then an aluminum scoop should be fine). Look into using pool noodles to create a basket you can dump your scoop finds in.. it'll float beside you in the river.