I don't have the Tigar Shark, but I do have the Sand Shark, and have used it in fresh water and at the ocean searching along the wet sand area and surf line.
I would highly recommend keeping the disc. turned down very low to avoid missing any gold rings.. believe me, they are out there to be found.
In my areas, there is not an over abundance of trash in the water .. the hairpins are the worst problem, but with the gold I have found since I started water detecting, I can put up with them too!
It is easy diggning in the sand and most items will not be that deep in fresh water ( recent losses ).
The saltwater beaches.. now that is a different story with the tides and deep sand.
You might as well be looking for a long handled scoop.. this will be needed if you go out in the water, and even in wet or dry sand it makes retrieving targets less tiring due to not having to squat down to dig.
Hope this helps some,
Felix