If you come out of the Blue Lagoon and are hungry you can go to the BL cafe, but it is expensive. Or you can drive back to Reykjavik, which is a fair distance if you are feeling hungry. Or you can pop down the road to Grindavik, and eat at the Mamma Mia. It isn't much to write home about, but the food is reasonable, and the prices reasonable as well - steak and chips for £12.50. My daughter said that the pizza was good, and the boxed the rest of it up for us and we ate it the next day. So we are glad we went there.