The underwater world looks different at night. In some oceans, plankton fill the waves with neon-blue sparkles, and jellyfish, shrimp and other creatures emit flashes or trails of light. You can cast your own glow with illuminated watercraft, or take a night dive to explore beautiful, bioluminescent flora and fauna.

If you've never been on the water at night, try a twilight tour on an SUP (stand-up paddleboard) equipped with waterproof LED lights. At Pirate Coast Paddle Company, in Newport Beach, California, you'll be guided through a calm bay as you look for sea lions, fish and bat rays swimming underneath your bright beams.

On the opposite coast, Aquaholic Adventures, in the Florida Keys, offers lighted kayak and paddleboard tours around Key Largo and Islamorada. These eco-tours start with a brief lesson on how to paddle. After you're underway, guides will point out the birds, sea creatures and mangroves you'll encounter. Book a full nighttime tour, or push off on a sunset tour. You'll leave in time to watch the sun sink below the horizon, and turn on your lights on the way back.

Endless Adventures Hawaii also launch tours at sunset. Their Glowpaddle adventures depart from the Ala Moana Beach Park on Waikiki. On Friday nights, paddlers can watch a brilliant display of fireworks onshore as they return.

For the ultimate in underwater viewing, try a Clear Kayak Night Tour at Adventure Center, in St. Thomas. These state-of-the-art kayaks have see-through bottoms and LED lighting to help you spot tarpon, rays and other marine life gliding below the waves. Guides conduct kayak excursions through a cove; into the mangroves on the east side of the island; or to one of several beaches.

If artificial lights aren’t your thing, opt for a bioluminescent experience. BK Adventure Eco Tours leaves from Merritt Island, Florida, for kayaking tours of the Indian River Lagoon. The glow you’ll see in the water comes from plankton and comb jellies that produce sparkles when the water around them is stirred up. Tours under a full moon are magical, but this phenomenon looks brighter when the moon is new and the skies are dark.

Mosquito Bay on Vieques Island, off the coast of Puerto Rico, is one of the brightest bioluminescent bays in the world. Guests at W Retreat & Spa – Vieques Island kayak out after dark into waves that glow blue from the light of marine micro-organisms. Bieque Eco Trips also partners with the retreat to offer a combination kayak excursion and laser pointer astronomy lesson. Puerto Rico has two other bio-bays, Laguna Grande and La Parguera, although the latter has lost some of its glow in recent years, probably from pollution and over-use.

For an up-close look at the glowing, underwater world, go scuba diving on St. Croix, in the Virgin Islands. Dive Experience, a PADI five-star dive training facility, trains and equips divers to visit a phosphorescent bay in the Salt River estuary. The light in this bay comes from micro-organisms and ostracods (tiny crustaceans). When the creatures are courting, they generate pulses of blue light that look like a string of pearls being illuminated, one after another.

Take note: specific skills and training are required before you can dive at night, so ask about PADI Night Diver speciality certification at your local dive shop or the resort you're visiting. Once you're certified, explore after dark with a flashlight, head lamp or other dive gear, or go on a fluorescence night dive. These dives, also known as fluo dives or glow dives, use special UV lights and mask lens filters to help you see incredible underwater pinks, blues and greens. (Think of how black lights bring out fluorescent colors, and you'll have the idea.)

The southern part of Koh Kong, an island off the mainland of Cambodia, is a great place to night dive. You're likely to encounter stingrays with electric-blue spots, moray rays and glowing cat sharks. On the islands of Koh Tang and Koh Prins, you'll find corals, trigger fish, large barracuda and crustaceans.

Fluo diving is also excellent on Bonaire, an island just north of Venezuela. Anemones, worms, fish and other marine life take on psychedelic colors when seen through your specialized UV light and yellow mask filter.

On the Caribbean island of Grenada, fluo diving is popular when you're exploring shipwrecks and the seahorses, sea turtles, orange cup corals and other marine life around them. The remains of a 600-foot former luxury liner, the Bianca C, lie here, but because the wreck is 165 down, this dive requires advanced skills and experience.

You'll find illuminated tours and night dive opportunities around the world. Avoid disappointment, and check before you go to verify schedules and seasonal availability.