How to reproduce the smell of the ocean in cooking?
"The smell of the sea" as romanticised by those of us who visit the shore infrequently, is really that of rotting seaweed &amp; dead sea animals... 

So, that aside, which aspect of "the smell of the sea" are you really trying to recreate?

It could be as simple as 'make it smell a bit fishy' for which almost any South East Asian fish sauce will do. [It will also add salt, so be careful in your seasoning]. Some are far stronger than others &amp; many, to a westerner, have almost indecipherable labelling, so you may need to try a few to find the right one. They're generally quite cheap, so it's not too hard to experiment.

Additionally, sea-weed - packaged conveniently in sheet form by many Japanese companies for making sushi - would add some of that 'vegetable edge' to the experience, with its own distinct aroma.

Both of the above, added to almost any broth or sauce, will set you off in the right direction, without having to add anything you dragged from the pier yourself ;)