Does 10 damage plus 10 more damage for each Energy attached to Poliwag but not used to pay for this attack's Energy cost. Extra Energy after the 2nd don't count.
In Japan, this card was reprinted with artwork from one of five winning entries of the CoroCoro Pokémon Snap contest held in Spring 1999. This version is extremely rare and the exact number in existence is unknown. This card was reprinted in the Base Set 2 reprint set, which was only released outside of Japan.
Trivia
The Japanese "Snap" print has a camera graphic where an expansion symbol would usually be.
The text on the bottom right of the "Snap" print reads: Best Photo Contest Winners Prize Card.