It is an island.
a island
a fresh water pond
pond
An island or if it is very big a continent
a fresh water pond
delta
peninsala
I think it is a peninsula.
a medium size body of water surrounded by land is a sea or a huge lake.
A peninsula is a body of land surrounded by water except for one connection to land. An isthmus is a narrow strip of land surrounded by water on both sides, but connected to land on both ends.
An area of land surrounded by water is called an island.
Land surrounded by water is an island . You are describing a peninsula.