I just started with liquid kelp that I bought at the healthfood store while waiting for my Lugol's to arrive by mail. It's been working fantastically well, and I feel very comfortable with it knowing it's an organic living food source. Not expensive either, an amount that will probably last a week or two (even by my exceeding the dosage form one drop to 5 eyedroppers full) and cost about $4.
Growing up a surfer in So Cal, I often would munch on seaweed floating by - especially when I was hungry but wanted to stay out and surf. Just another reason why hardcore surfers are in such good physical shape (even despite their hardcore partying).