Grammar Check: 'That river empties into the Gulf of Mexico' Is a Complete Sentence

Yes, "That river empties into the Gulf of Mexico" is a grammatically complete sentence. It is a declarative sentence—a statement of fact.

Structure Analysis

• Subject: "That river" (noun phrase with demonstrative adjective "that" modifying "river").
• Predicate: "empties into the Gulf of Mexico" (verb phrase).
• Verb: "empties" (intransitive verb, present tense, third-person singular).
• Prepositional Phrase: "into the Gulf of Mexico" (indicates direction/destination).
• Object of Preposition: "the Gulf of Mexico" (proper noun phrase).

The sentence expresses a complete thought: a specific river (identified by context or proximity) flows into the named body of water. No additional clauses or phrases are needed for grammatical completeness.