Activated abilities contain a colon. They're generally written "[Cost]: [Effect]."

Spells and abilities that target more than one Merfolk you control cost only more to cast or activate.

To determine the total cost of an opponent's spell that targets a Merfolk you control, start with the mana cost or alternative cost that player is paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Kopala's abilities won't affect triggered abilities (starting with "when," "whenever," or "at") that target a Merfolk you control.