Seaborn adventurer

Seclude (at the beginning of your upkeep you may
exile this creature under an island you control or return
this creature from exile if it is secluded. If this creature
is the only creature exiled under an island it is
secluded. Other player's cannot activate this ability).
When Seaborn adventurer enters the battlefield
create a treasure token.
{2}: Exile this creature underneath an island you
control. The mana cost of this ability must be
paid with mana from treasure tokens.