Underwater Scrap Activity

In the waters of San Andreas there are alot of old abandoned structures, boats, cars etc. It would be neat to be able to do an activity to go scrap these structurers and get different type of material from them. (Scrap Metal, Aluminum etc) Could also be a unique item that when turned into an NPC you can trade for items or materials (A fun way to gather mats for the mech shops?) Just seemed like a cool idea to ponder.