Yes, that's something like that some Japanese soldiers hiding inside the cave with some kinds of bushes cover around the tunnels, you know, you will not see anything at all - but they can see you from inside when you are coming outside from the beach.
Good thing that my grandpa told me that he never get landed on the beach because it was too many gunfiring and bombing everywhere near the beach, so all of US ships decided to turn around and shipped away from the beach. And, funny thing was some Japan warplanes started shooting machine guns and dropping some bombs on our ships!
Good thing they never did hit on my grandpa's ship he was on!!!
But very little inch bit because the bomb almost targeted on his ship - but MISSING!
He thanked to God for not getting destroyed on the ship, even drowned or get killed!