OCEANS     There are 4, given in order of size and percentage of total:

Pacific (46%), Atlantic (23%), Indian (20%), Artic (4%).
The "Antartic Ocean" is not a distinct ocean, being made up of parts of the Atlantic, Pacific, and Indian.

SEAS     There are 13, (you thought there were 7 ?) ranked in order:

Caribbean, Mediterranean, South China, Bering, Okhotsk, East China, Sea of Japan, Hudson Bay, North, Black, Red, Baltic, Yellow.

INLAND SEAS     are occasionally called lakes. In order:

Caspian, Black, Red, Aral

LAKES     The 15 largest, ranked in order:

Caspian, Superior (largest fresh water lake), Victoria, Aral, Huron, Michigan, Tanganyika, Great Bear, Baykal, Nyasa, Great Slave, Erie, Winnipeg, Ontario, Lagoda.

RIVERS     Longest, in order, with miles:
Nile (4,145), Amazon (3,900), Mississippi 3,741), Yangtze (3,430), Ob-Irtysh, Yenisey-Angara, Yellow, Congo, Amur, Lena, Mackenzie, Mekong, Niger, Parana (2,450)

CANALS     Longest, in order, with miles:
Baltic-White Sea (141), Suez (100), Albert (Belgium), Moscow-Volga, Kiel, Gota, Panama (51).

MISCELLANEOUS POINTS:
- Lake Victoria, the source of the Nile River, is bordered by 3 countries: Kenya, Tanzania, Uganda.

- The mnemonic for remembering the Great Lakes, in order, is: SHMEO.

- The Pacific Ocean covers more of the earth's surface than all the land put together.