Lake Kayangan, Coron Island.

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Accessible by a steep 10-minute climb, the crystal-clear waters of Lake Kayangan are nestled into the mountain walls; underwater is like a moonscape. There’s a little wooden walkway and platform to stash your things if you go for a swim. Don’t expect privacy or quiet, though, as the lake, an Instagram favorite, is overwhelmed by the cellphone-wielding masses during peak hours. To avoid the crowds you'll need to visit on a private tour early in the morning or late in the afternoon.