Seaweed as fertiliser

[Babru]

My dad, who lived in Ayrshire, collected seaweed regularly and added it as a mulch directly, or dug it in to his veg beds. Over the space of 25 years he turned the soil in his garden from almost pure sand with a tiny topsoil to wonderful, friable dark soil which grew great crops. He even put it on the lawn as a winter improver. There was never any issues with salt.
All free from seaweed washed up on the beach.

I'm not sure it is legal to cut living seaweed though, but gathering it for personal use, why not!