The dragon-thing diving is smaller than the dragons we have now. also the ice is a lighter blue than the unbreakable ones.

What this implies then, is that we will be seeing new kinds of dragons.

What I am curious about is this, can the dragons now actually dive into the water, there is also speculation in other threads that these might be underwater dragons, or was this just a cut scene?

If we have to fight dragons in the water we actually need a way to you know actually fight in the water, we need to use weapons and be able to use magic in the water even possibly shouts to be able to fend off dragons as it is right now we cannot even fend off a slaughterfiwh without so much as a dagger or touch spell.