Personally I think it would be better with more HP and a higher Retreat Cost for it to work with Heavy Ball, but as it stands now, two Retreat Cost
Cheapest Pokemon Japanese Challenge from the Darkness card list & price guide
The deck's win conditions include overwhelming your opponents with a massive merfolk army, or utilizing alternative win conditions such as Simic Ascendancy
Do what you would with Masterwork of Ingenuity and have a second copy
Hydro Bazooka does up to 160 damage with five energy attached, but can be deployed for 100 damage at just three energy, so there's potential to turn this around if the opponent's hand doesn't quite play how they had hoped
As for what cards you want to collect to upgrade, Id recommend picking up 5,000 Years in the Future packs