The Deep Dark Sea

The Deep Dark Sea enters the battlefield tapped.
{t}: Add {u} to your mana pool.
Overdraw {9} - Create a 6/6 blue Giant Fish creature token. Activate this ability only at the beginning of your end step,and if {u}{u}{u}{u} or more was added to your mana pool this turn. (This ability costs {1} less to activate for each opponent)