SpoilerReading fail. Rather large change on the result of the battle
Dave's knife hits a better spot this time, while Slasher taunts the pokémon. Pel fires off a barrage of attacks, piercing through it's hard shell, taking it out before it can fight back any more than it already has. Shortly after, your pokédexes identify it as a Cloyster.
SpoilerSummary:
Dave's Arms Attack hits for 5 damage
Mueki uses Enriched Water on Collin, healing 30 damage
Slasher taunts Cl for 40 damage
Pel launches a barrage at Cl for 39 damage
1000 XP each for Pel, Punipuni, Slasher, and Rhea.