nice forced perspective shot here! all done in camera.
anyway, an underwater science base is opened. a bunch of civilians show up and a little girl, Jenny, is selected to go with them. this really is not one of my favorite episodes, though I like the monster a lot.
underwater stuff is tricky, and usually shot "dry" with a blue filter or with a pane of glass holding water. this was done dry. as the sub takes it's guests to the base the airline is broken by a mysterious drill.
Jenny takes pictures, and Hoshino is assigned to keep her company. once the monster attacks the base and disables the oxygen, he also keeps her spirits up.
eventually it's discovered the giant drill fish Gubira is attacking (no reason given, it's just what monsters do) and Ultraman has his fight with it. apparently it can also breathe air for extended periods of time.
the Shredding Halo is used, but it proves ineffective. Gubira catches it and reverses it right back toward Ultraman, who looks rather surprised.
eventually he chops off the beast's drill and it dies as he zaps it with the Spacium Beam. Gubira is a cool monster, a fish, which is a rare thing. and look at the grumpy face it has!