Goat format ruling
Heart of Clear Water

Card effect (current official text)If the equipped monster's ATK is 1300 or higher, this card is destroyed. The monster equipped with this card is not destroyed as a result of battle or by the effect of a card that targets the monster. (Damage calculation is applied normally.)
Rulings
- You may equip this card to a monster with ATK 1300 or greater, but it will be immediately destroyed.
- If a monster equipped with this card has its ATK increased over 1299, by the effect of Rush Recklessly, etc., this card is destroyed.
- If your Relinquished or Thousand-Eyes Restrict is equipped with Heart of Clear Water and you its effect to equip it with a Monster Card whose ATK is 1300 or higher, Heart of Clear Water is destroyed.
- Your monster equipped with Heart of Clear Water is not destroyed in battle, but you still take any Battle Damage that would be inflicted to your LP by the attack.
- If you Special Summon a monster with Premature Burial or Call of the Haunted and then equip that monster with Heart of Clear Water, the monster will not be destroyed if Premature Burial or Call of the Haunted is destroyed. A monster equipped with this card can still be destroyed by effects that do not target, such as the effects of Fissure, Dark Hole, Smashing Ground, or Torrential Tribute. A monster equipped with this card cannot be destroyed by a card that targets, but it may still be declared a target. So the opponent may activate Nightmare Wheel or Snatch Steal targeting your monster equipped with Heart of Clear Water.
- Q: If a monster is equipped with "Ring of Magnetism" lower its ATK so it can be equipped with "Heart of Clear Water," would the "Heart of Clear Water" remain equipped to the monster if the "Ring of Magnetism" was destroyed? A: If the monster equipped with "Heart of Clear Water" has their attack rise above 1300 at any time, the "Heart of Clear Water" is immediately destroyed.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Goat forum — sourced change requests get reviewed.