I am sure someone with coarse fishing knowledge will give a more accurate response, but here goes my effort.
In coarse fishing the area you are casting into is called a swim. A swim feeder is a plastic or metal canister with holes in it that is attached to your trace. You pack ground bait, maggots, or whatever into the swim feeder and cast it into your swim.
The bait comes out of the holes in the feeder and "feeds" the swim. Therefore you get a fair amount of bait - right next to your hook. This scent explosion hopefully attracts fish into the area, who will then gobble up all the bait - along with yours with the hook in it.
People are now using them in sea fishing in exactly the same manner. I have tried it, but personally I just put some cut up bits of sponge in mine which I soak in fish oils or fish attractants to hopefully lure some unsuspecting 10lb cod to my bait. I'm still waiting for that cod though.
I have caught fish using the method, but I can't say I have had enormous success with it. However, if the fish are not there - nothing will attract them. I do think it is a good idea though and will continue experimenting with different recipies and concoctions.
Do a search on posts by Swellyman - he has posted some material on the subject some time ago.
i think if the fish were near your bait , surely they would take it anyway?
it probably works in course fishing because the fish are closer together anyway.
why not use it in sea fishing. anything that gives you an advantage is worth a try.
There are a few ways to attract fish from the beach. You can use small pva bags full of chopped up herring, very oily, tied to your weight for close in Bass fishing. You can bury old fish and meat offal at low tide. I have some spiral course fishing swimfeeders, which I pack with chopped up mackerel, bind on with bait elastic.
It all helps, the tide takes the large scent trail downtide, fish are attracted to it like a magnet. Your main problem these days is a severe lack of all species due to over trawling up to the beaches.