Shining Shoal — ruling 1

If the player or creature that was targeted is no longer playing or on the battlefield when the damage would occur, the damage isn’t redirected.

Shining Shoal — ruling 2

The redirection protects both you and your creatures from the source. If the source would deal more than X damage to multiple objects, you decide which damage is redirected until X is used up. For example, your opponent casts a spell that deals 1 damage to you and 1 damage to two of your creatures. If you cast Shining Shoal with X = 2, you can have damage to you and one creature redirected to the target, or you could have damage to both creatures redirected.

Shining Shoal : règles, fonctionnement et interactions (MTG)

Shining Shoal is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

You may exile a white card with mana value X from your hand rather than pay this spell's mana cost. The next X damage that a source of your choice would deal to you and/or creatures you control this turn is dealt to any target instead.

How it works : Shining Shoal

Original English text — Wizards of the Coast / Scryfall

#1February 1, 2005· Wizards of the Coast
If the player or creature that was targeted is no longer playing or on the battlefield when the damage would occur, the damage isn’t redirected.
No other card is named in this ruling.
#2February 1, 2005· Wizards of the Coast
The redirection protects both you and your creatures from the source. If the source would deal more than X damage to multiple objects, you decide which damage is redirected until X is used up. For example, your opponent casts a spell that deals 1 damage to you and 1 damage to two of your creatures. If you cast Shining Shoal with X = 2, you can have damage to you and one creature redirected to the target, or you could have damage to both creatures redirected.
No other card is named in this ruling.