sea, ocean
海 centers on the vast body of salt water covering most of the earth: the sea or ocean.
foreign; abroad; overseas
sea; ocean; waters
Hokkaido (island, prefectural-level administrative unit)
pirate
seashore; coast; seaside; waterfront; beach
Tōkai region (of Honshu; incl. Aichi, Shizuoka, Mie and southern Gifu prefectures)
navy; naval force
prawn; shrimp; lobster
Shanghai (China)
(sea) voyage; navigation; sailing; passage; cruise
(on the) sea; surface of the sea
ocean; sea
area of sea; waters
bottom of the ocean; seafloor; seabed
Sea of Japan
seawater; saltwater
deep sea; depths of the sea; ocean depths
southern sea
nori; laver; edible seaweed, usu. Porphyra yezoensis or P. tenera, usu. dried and pressed into sheets
swimming in the ocean; sea bathing; seawater bath; going for a dip in the ocean
Mediterranean Sea
beach; seashore; seaside; coast
channel (e.g. between two land masses); strait
coastal waters; adjacent seas
海 combines 氵 (water) with 每, which likely contributed the sound and originally depicted a body of water. The modern form keeps the water radical and the phonetic component 每.
The left side is water 氵, and the right side 每 looks like a person with a hat standing by the shore. Picture someone gazing out at the vast sea.
For カイ, imagine a kite flying over the ocean: kite -> カイ, soaring above the sea.