(Sea Delta isn't a spell.)
When Sea Delta enters the battlefield, return a land you control to its owner's hand.
, : Tap target artifact with converted mana cost X or less.
: Add or to your mana pool.
Sacrifice Sea Delta: Add or to your mana pool.
, 
: Tap target artifact with converted mana cost X or less.: Add 
or 
to your mana pool. or to your mana pool.
