Gravity Shield only stops two dragons. It isn't effective against 5 hp Pufferfish.
He's talking about the deck in the OP, which doesn't have puffer fish.
The deck is supposed to be slow on damage. The 'theme' is like you're playing in MUD. Everything takes longer..
If the damage output is increased.. this deck could be impossible, but as it stands, one Gravity Shield could hurt this deck. (every deck has to have some kind of weakness)
Arctic dragons will actually be slower because they're only powered by the mark. They just do more damage overall, once they're played. And there isn't really anything else to use the water quanta for. But you do make a good point about gravity shield completely stopping this deck, as otherwise it looks extremely difficult. Although no one really uses gravity shield against FGs....
I'm thinking this deck would be extremely annoying for anyone trying to farm FGs quickly to spin upgraded cards.