Take a kayaking trip under cover of darkness to see an otherworldly natural wonder in Fajardo’s Laguna Grande, on the northeastern tip of Puerto Rico. The lagoon’s waters are filled with microscopic plankton that light up with natural bioluminescence when they’re agitated. So with every dip of the paddle or movement of the kayak, millions of these organisms become illuminated, creating what looks like a swirling galaxy of stars beneath the water’s surface. This rare phenomenon is best seen on dark, moonless nights.