Destroy all face-up WATER monsters you control, then you can Special Summon WATER monsters from your hand, up to the number of monsters destroyed by this effect.
Rulings
Individual Card FAQs
You can Special Summon high-level WATER monsters with "Big Wave Small Wave", like "Levia-Dragon - Daedalus", "Suijin", or "Gogiga Gagagigo".
You cannot use "Big Wave Small Wave" to Summon "Special Summon-only" WATER monsters like "Aqua Spirit" or "Fenrir".
You cannot activate "Big Wave Small Wave" when there are no WATER monsters on your side of the field.
"The Legendary Fisherman" is not destroyed by the effect of "Big Wave Small Wave" if "Umi" is on the field, so he remains on the field.
After destroying WATER monsters with "Big Wave Small Wave" you can choose not to Special Summon any WATER monsters if you wish.
Spell|
Normal