You’ve probably heard of the Blue Lagoon in Italy and the popular tourist attraction with the same name in Iceland, but you might not know about the sea caves under Owey Island off the western coast of Donegal, Ireland. When the sun hits the cave mouth at the perfect angle, the water appears bright blue and the walls sparkle red, purple, orange, and pink in what kayaker, rock, climber, and guidebook author Iain Miller calls the “Blue Lagoon effect.” In a video taken by Miller inside the cave, the range of colors are on full display, particularly the impressive, glowing effect produced by the sun’s rays on the mouth of the cave.

Miller wrote on his website that “any object in the water looks like it is suspended in air… the whole effect looks like an explosion of light and is a surreal natural phenomenon to witness firsthand.” Catching the display in person isn’t easy. Miller and his team paddled out to the sea cave at around 5:00 AM then waited about an hour for the sun to illuminate the cave. The phenomenon is highly weather-dependent, however, as clouds rolled in after about 40 minutes, causing the magical effect to vanish.

To catch the phenomenon yourself, you’ll have to visit the Owey Island sea cave at sunrise during mid-summer. “With a little bit of planning, nautical guile, and good luck,” Miller said, “it is possible to visit almost any sea cave at the right time and conditions to witness this Blue Lagoon effect.”

Of course, visiting any sea cave can be dangerous and should be done with caution and a certain degree of nautical expertise.

H/T: Travel & Leisure