Waimea Bay Beach Park, a popular surfing spot on Oahu's North Shore, Oahu, Hawaii, USA

Cave of Poetry (Grotta della Poesia), Roca Vecchia, Lecce, Salento, Apulia, Italy

Woman swimming at the small beach of Perna inlet, Palmizana, St. Clement island, Hell's Islands (Pakleni), Hvar city, Hvar island, Croatia, Southeast Europe

Swimming pool of the Four Views Baia hotel, Funchal, Madeira island, Atlantic Ocean, Portugal

White chalk cliffs in Sarakiniko, Milos island, Cyclades, Greek Islands, Greece

Swimming pool of Dar Tantora The House Hotel, a renovated original mudbrick village in the oasis of AlUla, Medina Province, Saudi Arabia

Drone aerial view of Porto Katsiki, Lefkada island, Ionian Islands, Greek Islands, Greece

Porto Katsiki beach with turquoise water, Lefkada island, Ionian Islands, Greek Islands, Greece

Simos beach with turquoise water, Elafonisos island, Greece

Simos beach with turquoise water, Elafonisos island, Greece

View of the Washington Monument in Washington, D.C., United States of America

Nurse sharks (Ginglymostoma cirratum), being fed in shark and ray alley, Caye Caulker, Mesoamerican Barrier Reef, Belize

Nurse sharks (Ginglymostoma cirratum), massing in Hol Chan Marine Preserve, inside the Mesoamerican Barrier Reef, Belize

Southern stingray (Hypanus americanus) over sand in shark and ray alley, Caye Caulker, Mesoamerican Barrier Reef, Belize

Southern stingray (Hypanus americanus) over sand in shark and ray alley, Caye Caulker, Mesoamerican Barrier Reef, Belize

Southern stingray (Hypanus americanus) over sand in shark and ray alley, Caye Caulker, Mesoamerican Barrier Reef, Belize

West Indian manatee (Trichechus manatus), on the reef near Caye Caulker, inside the Mesoamerican Barrier Reef, Belize

Cave of Papafragas, Milos, Cyclades, Greek Islands, Greece

Bimmah Sinkhole (doline), near Tiwi, Sultanate of Oman, Arabian Peninsula

Turtle Bay, a popular sandy beach in Cooper's Island, St. George's parish, Bermuda, North Atlantic

Marmari beach with turquoise sea water in Mani Peninsula, Peloponnese, Greece

Plitra beach with turquoise water in Karavostasi in the south of Greece, Peloponnese, Greece

Simos beach with turquoise water, Elafonisos island, Greece

Simos beach with turquoise water, Elafonisos island, Greece

Diaporos island and Karydi beach with turquoise water, drone aerial view, Sithonia, Chalkidiki, Greece

Swimming pool, surrounded by sandstone rock structures, Our Habitas AlUla, oasis in canyons of the Ashar Valley, Medina Province, Saudi Arabia

Visitors swimming at beach, Suomenlinna island near Helsinki, Finland, Europe

Xwejni Bay, a centre for swimmers and divers, near Zebbug, Gozo, Malta, Mediterranean, Europe

Wadi Shab, canyon near Tiwi, Sultanate of Oman, Arabian Peninsula

Swimming pool, The Thousand Nights Camp in the Sharqiya Sands, formerly Wahiba Sands, desert region, Sultanate of Oman, Arabian Peninsula

Petrified forest, Agia Marina, Agios Nikolaos Geopark, beach with turquoise water in the south of Greece, Greece

Swimming at Cala (creek) Pedrosa, Montgri massif, Costa Brava, Catalonia, Spain, Europe

An adult thousand-spot grubfish (Parapercis millepunctatus), out over open sand off Bangka Island, Indonesia, Southeast Asia

Achilles tang (Acanthurus achilles), Rongelap, Marshall Islands, Micronesia, Pacific

Two spot Goby (Gobiusculus flavescens), swimming with indistinct dark background, St Abbs, Scotland, North Sea

Atlantic spotted dolphin (stenella frontalis) . A spotted dolphin with a small pink spot to the left side of its dorsal fin. Eastern Caribbean

Atlantic spotted dolphin (Stenella frontalis). Bimini, Bahamas

Foureye Butterflyfish (Chaetodon capistratus). Full side view shot with clear markings, Bermuda, Western Atlantic

Starry night octopus, Octopus luteus, foraging on coral reef at night, Malapascua, Cebu, Philippines, Visayan Sea.

Spinner dolphin, Stenella longirostris, Namu atoll, Marshall Islands (N. Pacific).MID0042

Bluefin trevally, Caranx melampygus, Ailuk atoll, Marshall Islands, Pacific

Split image of Smallspotted dart, Trachinotus baillonii, swimming along the sandy shore at dusk, Rongelap, Marshall Islands, Micronesia

French angelfish, Pomacanthus paru, Ilha rata, Fernando de Noronha national marine sanctuary, Pernambuco, Brazil (S. Atlantic)

Group of girls splashing each other and playing in a lake

Spot-Fin Porcupine Fish (Diodon hystrix) swimming above the sandy bottom, Great Barrier Reef, UNESCO World Heritage Site, Queensland, Cairns, Australia, Pacific Ocean

Sunbathing couple, sailboat in the distance, "The Baths, " Virgin Gorda Island, British Virgin Islands, Lesser Antilles, Caribbean

Group of girls splashing each other and playing in a lake

Guineafowl puffer (Arothron meleagris), dotted phase, San Benedicto Island, near Socorro, Revillagigedo Islands, archipelago, Mexico, eastern Pacific

Swimming pool, Riu Hotel, Cancun, Riviera Maya, Mayan Riviera, Yucatan, Mexico, North America

Diving from a dock at Kovacine Campground, with its concrete beach, swimming, and boat docks, Cres Island, Croatia, Europe

Resort Rabac in Labin, Istria, Croatia

Thermal spring in Saturnia with sulphur-containing water of the Monte Amiata Manciano Toskana Italien

Five colourful rubber ducks floating in water

Resort Rabac in Labin, Istria, Croatia

Raffles Resort, Canouan Island, Saint Vincent, Caribbean

Swimming pool at Vilureef Resort, Maledives

Beach promenade with the Kurhaus Hotel, pier and casino, Scheveningen, The Hague, The Netherlands, Europe

Young people having a bath at Pinamar beach, Buenos Aires province, Argentina

Two feet in a swimming pool

Beach promenade and the Kurhaus Hotel, Scheveningen, The Hague, The Netherlands, Europe

Resort with pool at the beach of Trou aux Biches, Mauritius, Mascarenes, Indian Ocean

Beach promenade and the Kurhaus Hotel, Scheveningen, The Hague, The Netherlands, Europe

Resort with pool at the beach of Trou aux Biches, Mauritius, Mascarenes, Indian Ocean

Water park with swimming pools, Puerto de la Cruz, Tenerife, Canary Islands, Spain

Resort with pool at the beach of Trou aux Biches, Mauritius, Mascarenes, Indian Ocean

Beach promenade, Scheveningen, The Hague, The Nethelands, Europe

Hawaii, female Whitley's boxfish (Ostracion whitleyi) swimming over coral reef

Diver and a Spotted porcupinefish (Diodon hystrix), Hawaii, United States of America

Hawaii, Pantropical spotted dolphin (stenella attenuata), swimming at the surface.