Buy @ TCGplayer
{U}{U}: For each attacking creature without flying, its controller may pay {1}. If that player doesn't, creatures you control blocking that creature gain first strike until end of turn.
Can be used more than once in a turn. Each time, the opponent can pay to prevent giving first strike to a creature, but this payment only stops the current activation and not future activations of Tidal Flats.
First Strike is granted to your creatures currently blocking non-Flyers when this effect resolves.
The payment is made when the Tidal Flats effect resolves.
