Floodgate

Defender
When Floodgate has flying, sacrifice it.
When Floodgate leaves the battlefield, it deals damage to each nonblue creature without flying equal to half the number of Islands you control, rounded down.

Denizen of the Deep

When Denizen of the Deep enters, return each other creature you control to its owner's hand.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Man-o'-War

When Man-o'-War enters, return target creature to its owner's hand.

Terminal Moraine

{T}: Add {C}.
{2}, {T}, Sacrifice Terminal Moraine: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.