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.
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.
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.
The goof item below may give away important plot points.
Crew or equipment visible
Wires controlling Barugon's head and tail are visible in a number of shots, such as: when destroying a building with his tail during his introduction, when following the car with the diamond-ray, or when being pulled underwater by Gamera. In most scenes, the point where the wire is attached to his head can also clearly be seen.