Breaching Hippocamp

Flash (You may cast this spell any time you could cast an instant.)
When Breaching Hippocamp enters, untap another target creature you control.

Drowned

Ancient Carp

Devouring Deep

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Araumi of the Dead Tide

{T}, Exile cards from your graveyard equal to the number of opponents you have: Target creature card in your graveyard gains encore until end of turn. The encore cost is equal to its mana cost. (Exile the creature card and pay its mana cost: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Drunau Corpse Trawler

When Drunau Corpse Trawler enters, create a 2/2 black Zombie creature token.
{2}{B}: Target Zombie gains deathtouch until end of turn.