To be honest, it's probably more useful in singles, since it lacks spread moves. I guess Surf and Icy Wind are decent moves, though a Weakness Policy is more effective with Surf. WP Tyranitar would be good, the only problem is that it cancels out Drizzle, rendering Swift Swim useless. On the other hand, Sand Stream boosts Tyranitar's Special Defense, allowing it to take Surf better. Adamant also complements Surf + WP.
Icy Wind can also be used for support, though it's not as useful with Adamant. The Speed drop is still very good though, so it's worth using.
So, I would use a WP Tyranitar, though maybe take out Pelipper. Of course you could lead with Tyranitar and Floatzel, activate the Weakness Policy, then switch to Pelipper for rain, and then switch back to Floatzel for Swift Swim and a Weakness Policy activation in the same match. It's a bit excessive though, not gonna lie.
4- SpA Life Orb Floatzel Surf vs. 252 HP / 0 SpD Tyranitar in Sand: 101-120 (25 - 29.7%) -- guaranteed 4HKO
Floatzel @ Life Orb
Ability: Swift Swim
Level: 50
EVs: 252 Atk / 4 SpA / 252 Spe
Adamant Nature
- Icy Wind
- Surf
- Protect
- Liquidation
Really the best set I could think of. It would be better without Adamant in doubles, to be honest.
Tyranitar @ Weakness Policy
Ability: Sand Stream
Level: 50
EVs: 252 HP / 252 Atk / 4 Spe
Adamant Nature
- Ice Punch
- Rock Slide
- Crunch
- Protect
Ice Punch is coverage, Rock Slide is spread damage STAB, Crunch is STAB, and Protect is if you want Floatzel to use Surf again.
Pelipper @ Damp Rock
Ability: Drizzle
Level: 50
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Protect
- Scald
- Hurricane
- Roost
Damp Rock for more rain turns. Protect is just for an extra turn in the battle. Scald is rain boosted STAB. Hurricane is STAB that can't miss in the rain. Roost is for healing.
For the last member, I'm not really sure what you would use. Incineroar is always a good choice in doubles due to Intimidate, giving fake bulk to your team. Of course, rain isn't the best weather condition for it. You could use Whimsicott for Prankster Tailwind support, plus its Fire weakness is neutralized in the rain...
Whimsicott @ Focus Sash
Ability: Prankster
Level: 50
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Taunt
- Dazzling Gleam
- Tailwind
- Protect
Focus Sash is for surviving a hit, though watch out for a double target. Taunt is to prevent set up. Dazzling Gleam is spread damage STAB. Tailwind boosts your team's Speed, which helps T-Tar a lot.
I'm not very good at doubles, so please tell me if these were bad suggestions, lol.
All of that being said, Floatzel is probably just too frail to preform well in the later stages of the Battle Tree, but it can be good if used correctly, in my opinion.
Hope this helps! :)
