Heart of Clear Water is a Equip Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Heart of Clear Water is Unlimited.
YGOPRODeck lists Heart of Clear Water for these formats: GOAT, OCG GOAT, Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Heart of Clear Water appears in Dark Beginning 2 (DB2-EN186) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Heart of Clear Water is about $0.17 on TCGPlayer (prices change frequently).
