This is one of the simplest and most delightful treats imaginable. Officially known as a Fucus Bath.
You’ll need some of the easily available wracks. Serrated wrack is particularly good. You take a couple of handfuls, rinse it to get rid of any critters and salt, and then put it into a hot bath. You can use a bag if you want, to hold the seaweed.
I had some serrated wrack from Dunbar and used a previously unwanted underwear washing bag (does anyone, ever, really need one of these?) which is nylon and net, so reusable.
After a few minutes of exposure to hot water, the wrack will release a lovely soothing gel that has nourishing, moisurizing and antibiotic properties. Take care, though, as it does make the bath quite slippery.
After use in the bath, the seaweed can be used for compost!