Conversation so far:
is the gulf of mexico an ocean or sea
The Gulf of Mexico is a marginal sea of the Atlantic Ocean.
what defines the Gulf of Mexico as a marginal sea
A marginal sea is a division of an ocean, partially enclosed by islands, archipelagos, or peninsulas, adjacent to or widely open to the open ocean at the surface.

Question: where does the gulf end
Self-contained rewrite: where does the Gulf of Mexico end