- O cabalo, Bueu
- Oak Park
- Oak Park
- Oakland Ridge
- Oasis
- Oasis
- Oberoi House Reed
- Observatory
- Obyan
- Occhio di Dio
- Occhogahama
- Ocean Diver Wreck
- Octopus Reef
- Octubre Rojo
- Odyssey Wreck
- Oedolgae
- Off Kadena Marine
- Office
- Ogan
- Oganzaki Lighthouse
- Ogi Port
- Ohinau
- Ohoba No.1 Crevasse
- Oike
- Oil Rig Reef
- Ojo de Agua
- OK Marine Pro
- Okikawa Maru
- Okinose W Arch
- Okinoshima Island
- Okirai Namiita Beach
- Okishima
- Oključna
- Okorotere Island
- Oksuz Ada
- Okubo Hama
- Olang Sanctuary
- Old Aquarium
- Old Cement Barge
- Old Fort
- Old Isaacs
- Old Jetty
- Old Man's Hat
- Old Man's Hat
- Old Pian Island
- Old Quarry
- Old Wreck Head
- Oliveira e Carmo (Wreck)
- Olivetta
- Olowalu Beach
- Olympia Maru
- Olympia Regattastrecke
- Omi-Maiko Nakahama Beach
- Omijima Island
- Onderwater Natuurpark Zegersloot
- One Finger
- One Rock
- Onna Point
- Oosterschelde, Bergse Diepsluis
- Oostvoornse Meer
- Oostvoornse Meer Slag Baardmannetje
- Open Ocean Habitat
- Opera House
- Orak Adası
- Orange Coral
- Orange Forest
- Orca Housereef
- Orchard Beach (A/k/a Captain Mike's Beach)
- Organ Loft
- Oriza Park Beach
- Orizaba
- Oro Verde (Bow)
- Oros
- Orud
- Osaki Batfish Reef
- Osaki Hanagoi Reef
- Osaki Lion Fish Palace
- Osborn Shoals
- Osborne Shoals
- Osezaki
- Osezaki Beach
- Osprey
- Otomi Beach
- Otter Cove
- Ottoman Anchor
- Oued Yquem Wreck
- 青海島内湾 (Oumijima Naiwan)
- Outer Pinnacle
- Outer Rock
- Outhouse Beach
- Outpost
- Outside Crystal Cove
- Outside Edge, Aliwal Shoal
- Overhang 16-20Mts
- Overhead Rock
- Overheat Reef
- Owase
- Owens Reef
- Owhiro Bay
- Oyashirazu
- Oyster Bridge
- Oyster Reef
- Oyster Stacks