I live by the sea as well, and use it a lot - There is so much to write the easy way is for you to visit :-
www.learn.eartheasy.com/2010/09/how-to-use-seaweed-to-mulch-your-garden/

it is a lot better than trying to explain it to you

i just gather whatever there is and sort out the string and feathers. Then I put it in a plastic box with open sides and leave it in the stream on the beach for a bit. If you have no handy stream you can hose it down or just leave it for the rain to wash the salt out. I use two boxes so one comes out of the stream to drain when I need to put the next one in.Bag it up in old compost bags when its stopped dripping.Then you can either use it as a mulch as it is or put it in the compost. If you spread it in the autumn most of it will have disappeared by spring.
There's no mystique, its very simple. If you want to mess about making liquid fertiliser as you would with comfrey that's up to you but the other way is much easier!