Mason would not allow the player to attach a water energy card to the benched Staryu instead of the active Goldeen on turn one because doing so would change his script in two ways: Goldeen would not be able to attack on turn one and Seaking would not be able to use Waterfall on turn two
When it resolves, you perform the actions after the dash
Elsa, The Fith Spirit, reintroduced the Legendary Elsa, Spirit of Winter, with a new Floodborn target, and Naveen proved to be a beautiful and valuable card for the right deck, though not quite as impactful as first imagined
Playing four Ponder is insane, and way too underplayed in my opinion
It also reads: "Spells you cast cost one less to cast for each card type they share with cards exiled with Cemetery Prowler." This means that if you exile a creature with Cemetery Prowler, your creatures cost one less to cast