Volrath, the Shapestealer

At the beginning of combat on your turn, put a -1/-1 counter on up to one target creature.
{1}: Until your next turn, Volrath becomes a copy of target creature with a counter on it, except it's 7/5 and it has this ability.

Snake Pit

Whenever an opponent casts a blue or black spell, you may create a 1/1 green Snake creature token.

Lurking Crocodile

Bloodthirst 1 (If an opponent was dealt damage this turn, this creature enters with a +1/+1 counter on it.)
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

The Pride of Hull Clade

This spell costs {X} less to cast, where X is the total toughness of creatures you control.
Defender
{2}{U}{U}: Until end of turn, target creature you control gets +1/+0, gains "Whenever this creature deals combat damage to a player, draw cards equal to its toughness," and can attack as though it didn't have defender.

Vivien's Crocodile

This creature gets +1/+1 as long as you control a Vivien planeswalker.

Grayscaled Gharial

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

Sandbar Crocodile

Phasing (This phases in or out before you untap during each of your untap steps. While it's phased out, it's treated as though it doesn't exist.)

Sewer Crocodile

{3}{U}: This creature can't be blocked this turn. This ability costs {3} less to activate if there are five or more mana values among cards in your graveyard.

Wardscale Crocodile

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Scaled Behemoth

Spined Karok

Vivien, Monsters' Advocate

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
+1: Create a 3/3 green Beast creature token. Put your choice of a vigilance counter, a reach counter, or a trample counter on it.
−2: When you next cast a creature spell this turn, search your library for a creature card with lesser mana value, put it onto the battlefield, then shuffle.

Algae Gharial

Shroud (This creature can't be the target of spells or abilities.)
Whenever another creature dies, you may put a +1/+1 counter on this creature.

Crocodile of the Crossing

Haste
When this creature enters, put a -1/-1 counter on target creature you control.

Crocanura

Reach (This creature can block creatures with flying.)
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)