This classification includes divers and deck hands other than "diving tender" support personnel who assist in diving activities such as line handlers and pump persons whether they are located on a vessel or on the shore. Crews of vessels and divers about are classified under the appropriate vessel classification. Applies to operations of companies engaged in cleaning oil spills provided the activities are conducted on navigable waters. Also contemplates marine wrecking and includes a permanent yard maintained by a marine wrecking company. Additional operations included under this classification are underwater demolition experts, installers of underwater oil or gas flow lines from drilling rigs to production platforms, companies engaged in the prevention of oil spills from a berthed vessel prior to and during the unloading of oil and diving activities in connection with sewer construction, underwater mining and sweeping operations.