Varesh, Ixalan's Living Fossil

Islandwalk
Each land is a Island in addition to its other
land types
Whenever you tap a land for mana, add {u}
to your mana pool, use this mana only to cast
Krakens, Leviathans, Octopuses, and Serpents.
"Captain, land ho!... I mean fish, WOAH!"