What it does
Hydro Pump is a Water-type special move with the highest base power in the Water special category. Accuracy is 80% — roughly one in five uses misses. That's better than Focus Blast's 70%, but in doubles' compressed turn structure, an 80% accuracy move still carries meaningful risk.
The trade-off versus Surf or Scald is straightforward: higher power, lower accuracy. Choosing Hydro Pump means you need the damage. If the target doesn't go down without the extra power, Hydro Pump is the pick. If you need consistent hits over multiple turns, a more accurate Water move wins.
In doubles, Hydro Pump is single-target — unlike Surf, which hits both opponents (and your partner at 0.75×). Single-target means full power against one Pokémon without any spread damage.
Who runs it
Empoleon (43% usage) uses it in Trick Room builds. High Special Attack plus Water STAB under reversed speed — hitting first with Hydro Pump for maximum damage is the water-type's primary output role. Flash Cannon and Scald are the other main options depending on team needs.
Greninja (43% usage) has high Speed and Special Attack. Moving first plus Hydro Pump's power means opponents often go down before they act. Protean gives it Water STAB when using the move. The combination of speed advantage and peak power makes Hydro Pump Greninja's most decisive hit.
Starmie (Water/Psychic) is fast and uses it as its primary Water coverage hit against targets weak to Water.
Slowking occasionally uses it for a high-damage Water hit off its Special Attack.
How to use it
In doubles, Hydro Pump is the choice when a lower-power Water move doesn't deal enough to KO the target. Single-target burst. The moment to use it is when the target needs to go down this turn and you have reason to think the hit lands.
For Greninja, the combination of high Speed and high Special Attack makes Hydro Pump a turn-ending move — it outruns most opponents and the damage finishes the job before they can respond. That's what peak single-target special damage looks like in action.
Under Trick Room, slow Water-types like Empoleon move first and deliver the maximum hit before the opponent's fast Pokémon can respond. Same concept, reversed speed mechanic.
Tips & strategy
Hydro Pump vs Scald: Scald has higher accuracy and a burn chance but significantly lower power. When the target has enough bulk to survive Scald, Hydro Pump is the correct pick. When you're in an attrition game and burn utility matters, Scald pulls ahead. Many sets carry one of each for different scenarios.
The 20% miss rate matters most in must-win moments. Avoid clicking Hydro Pump in scenarios where a miss ends the game — either have a backup plan or use a more accurate option in those specific turns.