Goofs

During the final battle between the monsters, Gamera is shown ramming Barugon near the head in close ups, but further down the body in long shots.

In the English version titled "War of the Monsters," the television announcer covering Barugon's rampage knows the monster's name immediately after Karen (who's watching the broadcast in an airport) first utters it to Keisuke. Barugon is referred to as "the new monster" in the broadcast in both the Japanese and international English versions.

When the jets come to attack Barugon, the wires holding the jets are visible.

When Barugon's following the car, a lamppost gets caught between his teeth and wobbles around, revealing it's a model.

When Gamera thaws out and flies up, the jets propelling him briefly set the Gamera prop on fire.

English language version: If Barugon's is harmed by water, how did he swim from the sunken ship to the shore without any difficulty? The translation neglects to mention that while he's vulnerable to water, it doesn't immediately kill him, just weakens him. It has also been suggested that salt water doesn't harm him as much as fresh water.

Keisuke is brought on the expedition because he can fly a helicopter, and lands the party in a remote village near the cave. Somehow, Onodera (who has no idea how to fly a helicopter) gets back to the ship despite having left Keisuke trapped for dead in the cave. It is possible he used their jeep to drive all the way back, but by the time he would have gotten there, the ship would have already left. It's not explained how he got back to the ship in time.