Requires

Sea Gate Stormcaller must be in hand. Eternal Witness must be in hand. Yavimaya, Cradle of Growth must be on the battlefield. High Tide must be in hand. Snap must be in hand. You control at least two Islands. Mana needed:

Steps

1. Activate an Island by tapping it, adding .
2. Cast Sea Gate Stormcaller by paying .
3. Sea Gate Stormcaller enters the battlefield, causing you to copy the next instant or sorcery spell you cast this turn with mana value two or less.
4. Cast High Tide by paying .
5. Sea Gate Stormcaller triggers, copying High Tide.
6. Resolve both High Tides, adding an additional whenever you tap an Island for mana this turn.
7. Activate a Forest Island by tapping it, adding .
8. High Tide triggers twice, adding .
9. Cast Snap by paying , returning Sea Gate Stormcaller to your hand and untapping two Forest Islands you control.
10. Activate both Forest Islands by tapping them, adding .
11. High Tide triggers four times, adding .
12. Cast Sea Gate Stormcaller by paying .
13. Sea Gate Stormcaller enters the battlefield, causing you to copy the next instant or sorcery spell you cast this turn with mana value two or less.
14. Cast Eternal Witness by paying .
15. Eternal Witness enters the battlefield, returning Snap from your graveyard to your hand.
16. Cast Snap by paying , targeting Eternal Witness.
17. Sea Gate Stormcaller triggers, copying Snap, with the copy targeting Sea Gate Stormcaller.
18. Resolve the copy of Snap, returning Sea Gate Stormcaller to your hand and untapping two Forest Islands you control.
19. Activate both Forest Islands by tapping them, adding .
20. High Tide triggers four times, adding .
21. Resolve the original Snap, returning Eternal Witness to your hand and untapping two Forest Islands you control.
22. Repeat from step 12.

Results