We went right as it opened at 9am, and there was a line of people waiting to get in, but once we were in, it didn't seem crowded.
I think I'd call it the whitish-blue lagoon. The silica from the hot springs coats the rocks and turns the bottom of the pool white, and with the water over it, it looks a little blue-ish. When we were there it looked mostly white though.
And another pic:
I guess that does look blue in the pictures.
The silica and algae that live in the hot springs and the lagoon are used to make cosmetics, much like the Ahava Dead Sea products.
Lotions that use the silica mud are supposed to restore youth to your skin and tighten it up. The algae formulae are supposed to be healing or something.
In the lagoon, there are a few wooden boxes around the sides that you can reach into and get some of the extracted silica mud and smear it on your face. It goes on almost clear and dries paper white. It's fun to see people lounging around with their masks on. Everyone does it--men, women, all ages.
I didn't bring my camera in, so here is a random pic of a guy with the mask on:
They also sell a bunch of more refined products in the gift shop (and a few other stores in Reykjavik)
My skin was really dry after bathing in the lagoon, so I went into the gift shop and sampled a bunch of face and body lotions :)
$59 Blue Lagoon Algae and Mineral body lotion
Helped a lot with my dry skin!
$69 Blue Lagoon Mineral intensive cream
Was thinner than I thought it would be, but worked well.
$40 Blue Lagoon shower gel
I didn't try this one, but it looks pretty.