Type Preview: Water

It's the most populous type in the game, with a full 120+ Pokemon represented, and it's one unreleased event legend away from being paired with everything. It's a solid type on offense and defense, except for the one part of the midgame. I can probably run two teams with all the Pokemon here.

These puns are starting to not hold Water.

Type Effectiveness:
Attacking: Super effective on Fire, Ground and Rock. Resisted by itself, Grass, and Dragon. No immunities.
Defending: SEd by Electric and Grass. Resists Fire, itself, Ice and Steel. No immunities on type alone.

Dual-types: Normal, Grass, Electric, Ice, Fighting, Poison, Ground, Flying, Psychic, Bug (temporarily), Rock, Dragon, Dark, and Fairy ingame. Postgame adds Ghost, Steel and (once they get around to releasing #721) Fire.

Probable Final Team:
Froakie/Frogadier/Greninja: Well, let's see, it's a starter, it's /Dark which is a useful STAB, and it's a ninja frog. Last time I used this thing it made Smash Brothers. Probable Final Moveset: Surf, Dark Pulse, Extrasensory, Grass Knot/Ice Beam depending on the situation

Marill/Azumarill: Note what's missing there; I'm not starting the run with it this time, so I can pass it up until Surf comes in and I can double back to Route 3 to pick it up in the pond. Anti-Dragon and designed to Aqua Tail Valerie into next week. PFM: Waterfall, Play Rough, Dig, Brick Break

Squirtle/Wartortle/Blastoise: Run-Mega, for one thing. Sadly, his extra Pulse moves don't come into play unless I breed it with a Clawitzer, so I'll have to make do with a somewhat oddball moveset. PFM: Water Pulse, Dark Pulse, Flash Cannon, Ice Beam

Lanturn: Main switchin for Electric-types - screw being immune, I get HP *back*. Also provides much tanking and suprisingly good versatility. PFM: Surf, Thunderbolt, Ice Beam, Dazzling Gleam

Remoraid/Octillery: It's been my favorite Pokemon for years and FINALLY I get to use it in a run. Fills in some key coverage holes. PFM: Surf, Flamethrower, Sludge Bomb, Psychic

Poliwhirl/Poliwrath: Solid phyiscal cleaner, don't need to be heavy on the Special end this time. PFM: Waterfall, Brick Break, Earthquake, Rock Slide

Other team members: If I get a good draw on Clawitzer I might swap Blastoise for a full Mega Launcher-abuser. I'm also considering options for a Water/Flying at least until we get past Ramos and The Route That Shall Not Be Named, and I'm truthfully leaning toward Swanna.

Why not use...?
Let's start with the previous teammates that don't make it: Starmie, Lapras, Barbaracle, Ludicolo and Gyarados. /pours a .40 In all seriousness, they didn't really provide the team balance I needed for the run.

As for the rest: (deleted due to absurd length)

A few prominent ones:
Vaporeon: Yes, even  Vaporeon got the sting of Eeveelution movepool shrinkage. Maybe when Move Tutors return.

Relicanth: Not enough physical variety again.

Bibarel: Is still related to Bidoof.

Major Battle Expectations:
Viola: Sheer power of Froakie should get me past Vivillon.
Grant: Type advantage does it, just have to be careful to avoid the Thunder Wave.
Korrina: By the time I get here, I should have access to high-powered Water Pulses *and* an Air Slash.
Ramos: The first of two problems... There's going to be a lot of Aurora Beaming and Air Slashing involved.
Clemont: Lanturn can actually sweep this gym provided I can get something in to deal with Heliolisk's Grass Knot.
Valerie: Going for the straight sweep with Azumarill based on Fairy resistances.
Olympia: Greninja goes off here.
Wulfric: It helps to be Ice-resistant, but there's a little Flamethrower and Brick Break action.

Rival: Getting past Chesnaught might be tricky until the late game when we start getting Fairy moves.
Team Flare: Aside from Manectric, we should be able to overpower it.
Elite 4: Finally, an E4 where I'm picking the first type based on what I'll have more fun beating.
Champion: MegaBlastoise v MegaGardevoir: WHO YA GOT?

Trainer:
Despite not using a Wailord, I have always looked at using some of these Pokemon as a white whale if you weeeeel. So call me Ishmael. As for the Pokemon, I'm thinking of a Captain theme... and not just a bunch of sea captains.