Crawdaunt

Hyper Cutter
Prevents the enemy from lowering this Pokémon's Attack. Increases Cut's area of effect.
Shell Armor
Prevents Critical Hits.
Type Tier
Water / Dark NU
Statistics
Min- Min Max Max+
HP
63
- 267 330 -
Atk
120
248 276 339 372
Def
85
185 206 269 295
SpA
90
194 216 279 306
SpD
55
131 146 209 229
Spe
55
131 146 209 229
Name Item Ability Nature

Swords Dancer

Leftovers Shell Armor Adamant
Moveset EVs
~ Swords Dance
~ Return
~ Hidden Power Rock / AncientPower
~ Surf / Crunch
188 HP / 188 Atk / 134 SpA

This is probably rather self explanatory, but you Swords Dance up and then kill things with Return and Hidden Power Rock (preferred over AncientPower due to PP reasons). Pick either Crunch or Surf if you're worried about things like Ghosts or Skarmory switching in. Surf will also stop Ground-types like Rhydon and Donphan from coming in to ruin your fun. Hidden Power Rock will also harm Ghosts quite a bit so whatever. This is about all Crawdaunt is good for.

Other Options

Knock Off, Endeavor, Taunt. Just by looking at these you could probably make some sort of stupid set to Endeavor a Blissey and then Taunt its Softboiled, but that's all the uses I can think up for Taunt on Crawdaunt. Knock Off always does some harm to a team, even if it's just knocking off a Suicune's Leftovers. This matters quite a bit in stall games, however.

EVs

Speed for sweepers is a good idea, but honestly Crawdaunt isn't that great so regardless you won't get much. Split between Special Attack and Attack as you would for a normal mixed Swampert as your Attack will be increased by Swords Dance anyways.

Opinion

I don't know why Nintendo would give us two Dark/Water-types and give them both mediocre Special Attack, but Crawdaunt and Sharpedo are both rather worthless in the standard metagame. Sharpedo tends to be better because of its superior Speed. If you want a Swords Dancer, things like Blaziken and Rhydon are far better than Crawdaunt.

Counters

Suicune will easily roar you, any STABed Electric attack will murder it, and things like Snorlax will smack it around, Swords Dance or not.