Silfra Snorkeling Pond is a popular and unique experience in Iceland where visitors can swim between two tectonic plates. The water in Silfra is extremely clear and cold, making it a visually stunning but physically uncomfortable adventure. It's recommended to book a tour in advance, as they fill up quickly, and be prepared to layer up with warm clothing before and after the snorkeling session. The tour includes all necessary gear and even offers the option to have photos taken underwater. While the experience may be uncomfortable, it's definitely worth it for the once-in-a-lifetime opportunity to explore this beautiful fissure.