a gulf!
A body of fresh water surrounded by land is a lake or pond.
A body of fresh or salt water of considerable size, surrounded by land
Lakes are inland bodies of fresh (sometimes salt) water that are larger and deeper than ponds. They are surrounded by land.
A lake is generally fresh water, where the ocean is salt water.
Yes: Intertidal zone
a fresh water pond
Lake
A lake.
A body of land surrounded by water is called an island. Australia is surrounded by water but not considered an island because it is far too big to be considered one.Edition: I think an island can be any size.
On land fresh, on sailboats salt water.
lake
estuaryYou will see the term defined various ways, including "a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea" and "the part of the wide lower course of a river where its current is met by the tides". But, this is almost certainly the term you are looking for. An estuary environment is where salt and fresh water are mixed.