Chunking
Captain Larry said it all, but most important: menhaden oil.
The way the oil, any oil for that matter, 'breaks down' the wave process on top of the water? That's another 'attractant' for the sharks, albeit as much visual as scent driven.
That 'calm water' effect that can go on for a mile behind your boat attracts bait, birds and sharks just like chum, as it 'stands out' from the rough water around it.
Holey moley, on the roughest days of sharking, that oil slick on top of the water can really show you where your slick is and how to position or reposition your baits, the boat (if you're using a drift bag or chute), etc. and keep you in the money.
Captain Bob