S glass , are you PANNING or are you doing treasure hunting? I dont know much about Hawaiis geology but Im not aware of any gold deposits or pegmatite veins . The isalnds are peridotite lavas and those arent very silica (or gold ) rich to segment into pegmatites that Im aware of.
If youre treasure hunting, Id look into getting an underwater metal detector (Whites makes a "Surfmaster" That we use for locating old anchors in shallow dock areas of MAine.)People use thes eto find coins and jewelry in the surf in warm areas (I believe HAwaii meets the criteria)