Rain Dance

Bronzong @Damp Rock Bold Levitate
252 Def / 252 Sp. Def / 6 HP
Rain Dance
Grass Knot
Hypnosis
Stealth Rock / Explosion
Set Up, Explode. Grass Knot for any Swampy leads.
Kingdra @Life Orb Jolly Swift Swim
252 Atk / 252 Speed / 6 HP
Waterfall
Outrage
Dragon Dance
Rain Dance

Simple Sweeper

Toxicroak @Life Orb Jolly Dry Skin
252 Atk / 252 Speed / 6 HP
Bullet Punch / Swords Dance
Sucker Punch
Earthquake
Poison Jab

Simple Sweeper
Latias @ Damp Rock/Life Orb/Leftovers Timid Levitate
252 Sp. Atk / 252 Speed / 6 HP
Mist Ball / Rain Dance
Energy Ball
Dragon Pulse
Thunder
Thunderer and support.

Gastrodon @Rindo Berry Modest Sticky Hold
252 Defense / 252 Sp. Def / 6 Sp. Atk
Stockpile
Surf
Sludge Bomb
Recover
Wall for most electric types. Rindo to stop OHKOs from grass moves, Sludge Bomb to maim or kill grass types.

Surskit @ Choice Specs/Wise Glasses Timid Swift Swim
252 Sp. Atk / 252 Speed / 6 HP
Giga Drain
Signal Beam
Water Pulse
Shadow Ball

Special Sweeper that actually works

I love Surskit, it is my new favorite pokemon. I wish they made a GOOD evolution of it instead of the ugly and almost useless Masquerain. Latias may be replaced by Zapdos, I think my Zapdos on my other team lives longer. Maybe a slightly defensive Swampert lead to set up Rain Dance, not sure.
Alternatives:
SubPunching Toxicroak
Toxicroak @ Black Sludge Jolly Dry Skin
Substitute
Focus Punch
Sucker Punch
Bullet Punch / Poison Jab / Earthquake

Zapdos @ Damp Rock / Wise Glasses / Leftovers Timid Pressure
Thunder
Heat Wave
Rain Dance
HP Grass

Latias replacer
Swampert @ Damp Rock Bold / Jolly Torrent
Earthquake
Stealth Rock / Waterfall
Roar
Rain Dance

Lead

What's the reasoning for using Surskit over another water-type? If it's only because it's your favorite Pokemon you might want to reconsider. I mean, Eevee is one of my very favorites but I definitely wouldn't bring one to OU.

If you REALLY want to use Surskit, try it out in NU. In OU, there are MUCH better Rain Dance Pokemon. Omastar, Kabutops, Raikou, Gorebyss, Ludicolo, Vaporeon...the list goes on and on.

Besides my Surskit, is my team alright? I really wish they had another Bug / Water type with Swift Swim... maybe another evo of it as an alternative to Masquerain, or a third evo... I'll replace it for serious battles but I just love it so much.

Sorry for not talking about the rest of the team, I was just baffled by the Surskit in OU part XD.

Let's see...

Bronzong should really have Rain Dance, Stealth Rock, AND Explosion. Stealth Rock is absolutely vital to net certain KOs with Kingdra (and others like Kabutops that may replace Surskit). At the same time, Explosion is needed to get the first sweeper out right away. The Rain Dance turns go quite fast so you want to use them well. If it was me, I'd replace Grass Knot since Explosion will take care of those Swampert leads anyway, right? But if you like Grass Knot, you could replace Hypnosis (I just like the idea of possibly getting something asleep although you shouldn't rely on it much).

Kingdra is pretty standard. You could consider dropping Rain Dance for Draco Meteor or Hydro Pump to hit physical walls like Skarmory and Swampert hard. After all, Kingdra should ideally be coming in when it's already raining (hopefully late-game!). And if not, Dragon Dance saves you.

Toxicroak isn't sweeping in OU without a boost so keep Swords Dance. Poison Jab is a really poor move in OU, replace it with Cross Chop (if you're using a fighting type, take advantage of the great STAB). Now that you have Cross Chop, you don't really need Earthquake since before you mostly needed it to hit steel and rock-types. Therefore, you can replace it with Taunt to stop things like Forry from getting in your way, Stone Edge to give you amazing coverage and hit Zapdos (who WILL be switching into you), or even Bullet Punch for extra priority.

In OU, Grass Knot should always go over Energy Ball UNLESS Vaporeon is a problem. But since Latias has Thunder I think it's safe to say that you don't need Energy Ball! Mist Ball is kinda useless, Rain Dance is much better (especially if you decide to drop it on Kingdra). You say the Latias is support but you're running an offensive EV spread without the powerful moves--I don't know, it just seems weird. Try something like Rain Dance/Thunder/Recover/Dragon Pulse with a bulkier spread and Damp Rock or lefties.

Gastrodon looks alright although he doesn't seem too threatening. There are SO many Pokemon who would love to switch in on him. Get rid of Sludge Bomb. You say you have it to take care of grass-types but the only ones in OU are Breloom and Celebi. You might do a bit to Breloom (not enough to kill it, though, which means it'll begin setting up) but Celebi is going to laugh at such weak non-STAB poison attacks. Instead of Sludge Bomb why not try Toxic? It works well with Gastrodon's bulk and still threatens most grass-types AND bulky water-types (remember, those could counter your current set too). It's true that you have a slight Breloom weakness but Gastrodon is never going to fix that. Instead, rely on Latias and Toxicroak to take care of the grass types you seem concerned about.

Surskit should be replaced for an offensive Calm Mind Raikou (something like Calm Mind/Thunder/Hidden Power Grass or Ice/Shadow Ball), Swords Dance Kabutops, or maybe even Rotom-W (STAB Thunder, boosted Hydro Pumps, natural bulk, and the ability to help out with Breloom all in one!).