Lemuria, the Forgotten City

Field Spell

This card's name is treated as "Umi". All WATER monsters gain 200 ATK and DEF. Once per turn, during your Main Phase: You can have all WATER monsters you currently control gain Levels equal to the number of WATER monsters you currently control, until the End Phase.

Rulings – Yugipedia

Printings:

Abyss Rising: ABYR-EN057 (Common) - 2012-11-09
Legendary Duelists: Duels From the Deep: LED9-EN055 (Common) - 2022-06-16

Prices:

Cardmarket: 0.03 €
TCGplayer: $ 0.15