General:
* Sea
* Ocean
* Water
* Deep
* Abyss
* Expanse
* Horizon
* Surface
* Depths
* Shoreline
* Coast
* Beach
* Tide
* Current
* Wave
* Foam
* Spray
Specific Features:
* Reef
* Island
* Inlet
* Bay
* Strait
* Gulf
* Channel
* Cape
* Peninsula
* Lagoon
* Atoll
* Fjord
Wildlife:
* Marine life
* Fish
* Whale
* Shark
* Dolphin
* Seal
* Turtle
* Coral
* Seaweed
* Plankton
More Poetic/Descriptive:
* Azure
* Indigo
* Turquoise
* Emerald
* Sapphire
* Silver
* Blue
* Green
* Salt
* Mist
* Breeze
* Storm
* Tempest
* Gale
* Thunder
* Lightning
* Sun
* Moon
This list is not exhaustive, but it gives a good starting point for describing the sea. You can use these nouns in different combinations to create vivid and evocative imagery.