Aelindra, Eternal Tides

Waterborne Vitality (Whenever you cast an instant or sorcery spell, create a 2/2 blue Elemental creature token with "This creature has haste and vanishes at the end of the turn.)

Summon the Tide ({2}{u}{u}, tap Aelindra: Return all creatures you don’t control to their owners’ hands. Activate this ability only if you’ve cast two or more spells this turn.)

Grace of the Tides (As long as you control three or more Elementals, Aelindra can’t be blocked.)