Call me a spoilsport but imo seaweed is not the best mulching material as it
'dissolves' away to very little, when rain gets on it. It's certainly very
good for nutrients though

I know an urgler who uses it extensively on her garden and the results
speak for themselves. She has the most beautiful, well nourished
garden and I was lucky enough to see a new bed that she had created and
mulched with cardboard and seaweed, a lot of seaweed!

I'm no expert gardener but I am hoping, that, not only will it add
nutrients but that it will improve my heavy clay soil