Rate my Water-based team

[Dark Type Fan]

There's this Gym Leader championship and we must use at least 3 Water-type Pokémon in our teams. This means a lot of Ludicolos, Wash Rotoms, Greninjas and other Water types who don't have Grass- and/or Electric-type weaknesses. Other rules are the same as Nintendo's: no legendaries, but everything else is allowed (anarchy).

So I build my team, looking for a balance between sweepers and bulky Pokémon, and physical and special-based monsters, while trying to minimize disadvantages.

THIS IS MY TEAM:

Ludicolo @ Leftovers
Ability: Swift Swim
EVs: 252 HP / 128 Sp.Atk / 128 Speed
Nature: Calm
- Giga Drain
- Leech Seed
- Rain Dance
- Focus Blast

Azumarill @ Sitrus Berry
Ability: Huge Power
EVs: 252 HP / 252 Atk / 4 Speed
Nature: Adamant
- Belly Drum
- Aqua Jet
- Superpower
- Play Rough

Starmie @ Leftovers
Ability: Natural Cure
EVs: 252 Sp.Atk / 128 HP / 128 Speed
Nature: Timid
- Rapid Spin
- Thunderbolt
- Psyshock
- Recover

Scizor @ Life Orb
Ability: Technician
EVs: 252 Atk / 252 Speed / 4 Sp.Def
Nature: Adamant
- Swords Dance
- Acrobatics / Pursuit
- Bug Bite
- Bullet Punch

Gengar @ Gengarite
Ability: Levitate / Shadow Tag (Mega)
EVs: 252 Sp.Atk / 252 Speed / 4 HP
Nature: Timid
- Shadow Ball
- Sludge Bomb
- Energy Ball
- Thunderbolt

Tyrantrum @ Life Orb
Ability: Strong Jaw
EVs: 252 Atk / 252 Speed / 4 HP
Nature: Jolly
- Stone Edge
- Earthquake
- Rock Polish
- Fire Fang

Should my Tyrantrum have Stealth Rock instead of Rock Polish? Should I try for a Trick Room team with Slowbro? Should I go for Scizorite instead of Life Orb on my Scizor? What should I change, if anything?

Remember this is a Water-based championship I'm going for, so it means a lot of Water-types and their counters (Grass- and Electric-types).