Pet Battle: [3-4] Westfall; [3-6] Azshara; [20-22] Howling Fjord; [20-22] Borean Tundra; [23-24] Twilight Highlands;  Nagrand (Draenor)
Pit-pattering footsteps; vocalizations (on-click)
100% Hit Chance
Snaps at the enemy, dealing 394 Beast damage.
100% Hit Chance
Rushes to the enemy on a stream of water, dealing 295 Aquatic damage.
This move always goes first.
Fills the area with a healing mist, causing your front pet to restore 157 health every round.
Lasts 3 rounds. Persists through pet swaps.
Restores 591 health to the user.
Reduces up to 98.5 damage from each attack against you.
Lasts 5 rounds.
Causes a whirlpool to form under the enemy pet.
In two rounds, the opponent's pet will take 591 Aquatic damage and be rooted for 2 rounds.
Harmful damage over time effects are reduced by 50% on Aquatic pets.
50% from Flying abilities
33% from Undead abilities
If you are just starting to level battle pets, level this guy first. He can easily level all your other pets by himself. Crabs in general are a great idea when first starting out.
Keep Shield Shell up all the time, recast when it's at 1 round
Keep Renewing Mists up whenever you're at less than 7/8 HP
Recast Shield Shell anytime your oponent burrows or is otherwise unavailable to attack
It'll take a bit of bad luck to come out of combat with less than full health
Whether it's a good pet or not, I caught my rare one today in Krasarang Wilds, in The Deepwild, while leveling my Disgusting Oozeling and Phoenix Hawk Hatchling with my Emerald Proto-Whelp, still my favourit.
Seen all your comments I wanna find out if it beats my Proto-Whelp :)
One of the best pets for leveling others and fighting epic, legendary, artifact, and beasts of legend pets.
This pet is my #1 pet so far. Great for leveling other pets when it hits 25. Combination of the sheild (c-ya later dots!) and healing is great for not having to bandages or revive after battles. I highly recommend finding a rare Shore Crab, Strand Crab, or Strand Crawler to help with leveling other pets. I has even become an all star in pvp pet battles.
I love this guy, he is my number three, rotate throught the other two slots the ones I want to level, then bring in this guy to clean up. Shell, mist and then snap. Also good to cast mist if need to bring cockroach back on for armaggeddon and health a little low.
I cannot even begin to guess why this one is ranked so low. It's unglamorous, perhaps? In any case, the venerable Shore Crab is a powerhouse for leveling and for taking on tough tamer battles. It tanks and its multi-turn front-line heal keeps squishier higher-DPS pets going. And it is common enough that you can grab a decent one in most areas of Azeroth for whatever level range you need.
This crab became my premier battler very quickly when I found out I could take on 3 x level 11's at level 8.
My new strategy became capture higher level pets to use on his team as back up. Still, I had very little cause to call on them with "Lefty" at the helm.
I noticed the guy above stated mist before shell, I feel since shell lasted longer, start shell, then mist so you have 3 uninterupted rounds of snappage before having to refresh.
This guy is a crazy good tanking and power levelling pet. I take Snap (critter dmg), Healing Wave, and Shell Shield. I start combat with Shell Shield up - maintain that, and snap my way to victory with occasional healing waves. I like to use this guy around Half Hill with a low level pet in my group, I start combat with that pet and then kill everything with the crab. With +dmg to critters you clear a team in no time with very little loss of health overall.
I found a whole bunch of them underwater in Silithus. Tossed on my Kalu'ak Fishing Pole and dived in. Unfortunately, every single one of them keeps telling me "pet battle area is obstructed".
UPDATE: the bug where you cannot initiate combat while swimming is known and WoW is actively working on it.