Once during your turn (before your attack), you may attach as many basic Energy cards from your hand to any of your Pokémon in any way you like. If you do, your turn ends. This power can't be used if Blastoise is affected by a Special Condition.
Hydro Pump ハイドロポンプ
Does 50 damage plus 20 more damage for each Energy attached to Blastoise but not used to pay for this attack's Energy cost. You can't add more than 40 damage in this way.
This card later received an erratum to change the Waterlog Poké-POWER to clarify that using the power ended the player's turn and wasn't an effect of the Poké-POWER. The start of the text was rewritten as "Once during your turn (before your attack), you may use this power. If you do, your turn ends. Attach as many basic Energy cards from your hand to any of your Pokémon in any way you like."
The Waterlog Poké-POWER is essentially a more balanced, watered-down version of the Rain Dance Pokémon Power possessed by Base SetBlastoise, a power so strong that it spawned one of the most popular deck archetypes of the Base Set era, Raindance. The requirement of ending your turn effectively prevents Waterlog from being as dominating a force as its predecessor.