- U-1105 "Black Panther" German U-boat Sub
- U-1277, wreck
- U-455
- U-Boot (Wreck)
- U rigonne
- Uchizan
- Čuf
- Ugan
- Uguru Island
- Ukibaru North
- Uklia
- Ukumbe Reef
- Ullastre I
- Ullastre II
- Ullastres
- Ullastres Iii
- Ulong Channel
- Ulua Beach
- Ulysses, wreck
- Um Almaradem
- Um el Faroud
- Um el Faroud - Oil Tanker
- Um El Sheikh
- Um-faroud
- Um-faroud, Wied Iz-zurrieq (Sur)
- Um Halhalla
- Um Khararim (Cave Reef)
- Um Sid
- Umagai
- Šumaricko jezero
- Uminchu
- Umm El Ros/Marsa Mubarak
- Umm Gamar
- Umm Usk
- Umma Gumma
- Under Pressure Weyregg
- UnderSea Adventures Training Pool
- Underwater Forest
- 潘家口水下长城underwater Great Wall
- Underwater Habitat by Sub Oceanic at Hilton Maldives
- Underwater Military Museum
- Underwater Museum of the Arts
- Underwater postbox 海底郵筒
- Underwater Sculpture Park
- Underwater Statue Alley
- Underwater Triglav
- University - האוניברסיטה
- Unjang
- Untergrombach (Metzgerallmend)
- Unterwasserwald
- Unterwilen
- Untiefe Maria Wörth
- Upcoming Divespot Amersfoort
- Upper Comal River
- Urabain, Wreck
- Urban Sports Pool
- uren Harbor 漁人部落港灣
- Urfeld
- Urfeld - Desselwand
- Urisee
- Ursus (Wreck)
- Uru no Sachi
- Usami Beach
- Usami Kagone
- Usami Manbo Point
- USAT Liberty Wreck
- USCG Bibb (Wreck)
- USCG Duane (Wreck)
- USS Chickasaw
- Uss Emmons
- USS Kittiwake (Wreck)
- USS Massachussets
- Uss Oriskany
- USS Oriskany Wreck, Pensacola, Florida
- USS Spiegel Grove (Wreck)
- USS Strength (Wreck)
- USS Tucker
- USS Vandenberg (Wreck)
- Žusterna
- USTS Texas Clipper TPWD Wreck, Texas
- Usujiri Jinjamae
- Utheemu Reef
- Uthuru Ethere Faru
- Uthuru Faru
- Uthuru Maafaru North Corner
- Utopia Beach House Reef North
- Utopia Beach House Reef South
- Uvala Polje - Zid
- Uvala Slana
- Uvala Zakenj
