As a longtime kaiju fan, Kaitei Gunkan has always been my favorite....I saw it for the first time in LA back in '66.
What's always bugged me about Tsuburaya, Eiji's spfx is that he'd do one scene that was a knockout (and there are a lot of 'em in this film) and then one that really sucked.......Such in this film is the sequence with Monda the dragon, as he attacks the sub.
I'll give them credit for attempting to "animate" an oriental style dragon but the execution is pathetic! Obviously a puppet - wires and all, he moves like one of those cheesy costumes in a Chinese new year's parade or one of those articulated bamboo dragon toys I used to see in Chinatown...In some ways it really comes close to ruining the film - and that's a tough order!
This is one time I wish someone'd do a Lucas and go back and modify the scene digitally to where I don't have to hide my eyes until it's over!
Monda appears again in "Big Monster Battle" (Destroy All Monsters) in '68. At least here he's on the ground and moving like a snake, not suspended....And, on screen for only a brief moment - thank god!