Buoys for this use are usually either inflated and sealed by a valve or cap, or made from buoyant material, so they do not deflate or flood during the dive, rendering them ineffective.
The DIR diving philosophy considers unsafe any attachment of the diver to equipment or objects which end above the water surface, due to high risk associated with dragging the diver upwards in spite of their decompression obligation or maximum ascent speed limit [REF].