It only takes the gentle brush of a hand or slow glide of a boat to trigger the sparkling blue-green light of bioluminescent plankton, or phytoplankton. The dinoflagellates — single-celled phytoplankton that produce oxygen in water — emit a sparkling cold light when agitated as a protection mechanism.

This unpredictable category of glowing marine life, however, is known to play a ruthless game of ‘right place, right time’ with those eager to observe it. Occurring predominantly in the deep waters of the world’s oceans, and only rarely on shallow coastlines, the phenomenon requires warm, calm and windless waters, as well as low-lit new moon nights, to ensure particularly memorable displays.

Due to the fragility of the phytoplankton, scientists recommend observing the spectacle from a distance. The silver lining? If one blue tide washes ashore, it’s likely to stay for another night or two. From Australia to Wales, here are the best places to witness bioluminescent tides yourself.

There’s no denying that Puerto Rico’s Mosquito Bay is the world’s brightest bioluminescent bay — it was officially recognised as such by Guinness World Records in 2006. A designated natural reserve, its mangrove-fed abundance of dinoflagellates doubled in 2017, after Hurricane Maria overwhelmed Puerto Rican shores. With its ideal low-light conditions, the bay is a true sight to behold, hosting the breathtaking underwater show year-round.

Equally as captivating are Fajardo’s canal-like Laguna Grande, close to the capital San Juan, and La Parguera, located in Lajas, which is the only Puerto Rican bio bay where motorboats and swimming are allowed.

New South Wales, Australia

Jervis Bay, along the southern coast of New South Wales, is known for its sweeping beaches, the aptly named White Sands Walk and first-class whale-watching — the national park really has it all, including phytoplankton. Covering 39sq miles, Jervis Bay has several locations where this magical lightshow has lit up the waters in the past. Informed guesses would point towards Barfleur Beach or Blenheim Beach, where the bioluminescence typically blooms between May and August. However, if the right weather conditions prevail, it can be seen year-round — locals news is the best source of information to catch potential blooms.

Jarvis Bay in New South Wales is Australia’s likeliest location for bioluminescent tides to occur.

Krabi, Thailand

When it comes to dazzling blue waves, the Thai province of Krabi in the southwest of the country is another great destination to visit. Home to shallow waters, mangrove forests and coral reefs, the coastal areas of Krabi provide the perfect conditions for dinoflagellates to thrive. The province’s tourism board runs seven island sunset and plankton tours and even advises on which dates to target for the ultimate glow experience. A good rule of thumb, however, is to make the journey between November and May when there’s little to no rainfall. Staying on the western side of Railay Beach, one of the most popular sites for bioluminescence, is another way to witness the maritime lightshow right from your bungalow.

While bioluminescent plankton has many nicknames across the globe, the Taiwanese version is perhaps the most evocative. On Taiwan’s Matsu Islands, located just a few miles shy of the eastern coast of China, the glowing microalgae are known as ‘blue tears’ and are said to be spotted in higher concentrations during the short window from April to June. Beigan, in the north of the island group, houses one of two local airports and offers the highest success rate of seeing the glowing tides. Boat tours around Qiaozi Village and Beigan’s western shores leave every day at dusk, and while bioluminescence is never guaranteed, most visitors are lucky enough to see the brightly lit waves.

Beigan, in the north of this Taiwanese island group, offers the highest success rate of seeing the glowing tides.

Oaxaca, Mexico

There’s already a very specific list of conditions needed for bioluminescence to occur, but in Puerto Escondido’s Laguna Manialtepec, another crucial factor must cooperate. It’s only during the rainy season in June and July, when the lagoon connects to the ocean on Mexico’s western coast in Oaxaca, that the plankton can seek refuge in the tangled mangrove riverscape. Once there, however, the calm and warm waters prove perfect for hosting twinkling ripples in the pitch dark. Most boat tours leave for the lagoon at 1am, but the sleepless night is worth it — you’ll also be able to look out for the native crocodiles lining the canal’s edge.

California, US

Most of California’s beaches are already breathtaking by day, but stay after dark and the show could continue with blue, sparkling sand and water. At San Diego’s Mission Bay and Newport Beach, flare ups of bioluminescent plankton have recently increased from ever few years to three years in a row. Last year’s unprecedented waves captured social media attention with the help of local creator Patrick Coyne, who partnered up with Newport Whale Watching to offer impromptu boat tours on lit-up nights. While October and November proved to be by far the most active months, it’s difficult to predict if this lucky run will repeat itself in years to come. Those willing to take the risk, though, might just be rewarded with sapphire-bright beaches.

Southern Californian coast has unexpectedly enjoyed bioluminescent tides for three years in a row.

Wales, UK

Perhaps the most unlikely of locations for sparkling tides to wash ashore is the rocky and windswept coast of Wales. Granted, the likelihood of stumbling across this natural phenomenon, which seems to have a tropical preference, is significantly lower here, yet nowhere near nil. In recent years, and most likely due to climate change, nighthawks have spotted blooms of bioluminescent plankton here — Dunvegan Bay in the northwest and Anglesey’s Penmon Point are likely locations to spot high concentrations during mid to late June. Should luck be on your side, skip a stone across the surface and admire the otherworldly glow cascade out into the open sea.