The hellbender prefers clear fast-flowing larger streams and rivers with rocky bottoms and plenty of cover in the form of logs and debris (Behler and King 1979).
Aquatic Biomes: rivers and streams
Medium to large slabs of rock sloughed from the bedrock tend to provide the best shelters. These rocks must be resting atop sand and gravel rather than embedded into he river bottom. Small dug-out openings along the downstream edge of the rock are a good indicator that the rock is being used.