When Marsh Crocodile enters the battlefield, return a blue or black creature you control to its owner's hand.
When Marsh Crocodile enters the battlefield, each player discards a card.
10/4/2004 Both triggered abilities trigger at the same time so you can decide which order they go on the stack.
10/4/2004 This card can return itself to your hand.
10/4/2004 You choose the creature to return on resolution of the triggered ability. This is not targeted.