Such is an improper use of the term as noted by the definition.
True. However, my point was just that we can't be assured that the formal, strict definition of the word is the proper usage here.
That such the colloquial usage is improper doesn't stop it from being used, especially considering that no one ever seems to be speaking about the Sea of Eden in a formal sense. Seas are such variable things and there are enough instances of "sea" being used colloquial (in the real world, at least) in order to question such a strict interpretation.
And to note, the Sargasso Sea is still a sea, given its unique nature compared to surrounding waters.
Perhaps quotes from the game might help me make my point?
The Dead Sea is an ocean
located to the east,
surrounded by coral.
It used to be called the
Sea of Eden, but even then,
not many dared enter.
We investigated the area,
but to no avail.
We could find no entrance.
That ocean was called
the Sea of Eden until
3 years ago...
This may just be the
clue we were looking for.
Once we uncover Lynx's plans,
it should be easy enough to
counter them.
Originally, El Nido was
nothing but ocean.
Rumor has it
that a star fell into
this ocean, along with
a star child.
Perhaps that child
is alive somewhere?
Either "ocean" or "sea" is clearly being used colloquially (possibly both).
That the waters around El Nido were once (and to an extent, still are) considered part of the ocean doesn't preclude the possibility that El Nido is in the location you are proposing, but it also doesn't necessitate that they were anywhere near a shore. Given that Chronopolis was a secret installation, I am inclined to believe it was located in a more remote location, but that is just that, an inclination.