Dive Sequence Help

[Memory Master]

So I got my copy of KH3D the other day and I'm trying to get to The Grid with Sora. However I seem to be having trouble against the octopus boss you have to face during the dive sequence. I'm trying everything I can but I can't even damage it. Anybody know what i'm not doing right here?

 

[Cosmic+Amarna]

You have to hide behind the boulders and wait, then a part of it will get really close to you. Then you can damage it.

 

[maggosh]

You have to hide behind the boulders and wait, then a part of it will get really close to you. Then you can damage it.

Hmm, sounds suspiciously similar to the Vanitas Remnant strategy...

 

[Memory Master]

You have to hide behind the boulders and wait, then a part of it will get really close to you. Then you can damage it.

Obviously I'm just not getting something here because I stay behind the boulder when he uses it but I'm still not doing damage to him. What attack should I use and what should I be aiming at because this is starting to get frustrating.

EDIT: Nevermind, I finally figured it out. Thanks for the help.