I'll be honest, I didn't really read much of this, but I've been working on a mono-water team for a while, and it's a really fun experience.(EDIT, I read a few of the later pages when the team was being tested, and found a lot of the comments to be in-line with a lot of what I noticed. Also, wtf Galvantula? LOL)
Use Swampert. Unaware Quagsire can also be useful, but I feel like an idiot just saying it; they cover electric and doesn't afraid of much but grass. They can also benefit from a Trick-Room from Slowbro, as a lot of Bulky Waters tend to be on the slower side (Swampert, Bro himself, Vaporeon, and the list goes on - the only thing that stops a full Mono-Water trick-room team is a lack of pokes to set it up -I think-)
Use Vaporeon, to wish Swampert when he needs it. Face it, as cool as Hydration/Rest is, Wish benefits your whole team, especially because Vaporeon is one of the best wishers you can find, and it doesn't get shafted by opposing weather. Give it ice-beam to cover the grass weakness he has, and Scald to provide burn. Water is ALL ABOUT BULK, so go with Acid Armor too. It sounds strange, but a good chunk of your supportmon should have Scald as their primary stab, so if you combine that with Vappy's huge HP, acid armor just leaves all of their physical sweepers useless.
A good Slowbro is bro-tier too - I can't stress how good and annoying he is, but you all know that. So many options. He can run Flamethrower/Fire Blast, Focus Blast, Thunder Wave, his movepool is SOOO gravy.
Ludicolo is a good choice, being neutral to both Grass and Electric, as well as fire, his typing sort of runs contrary to the rest of the teams. His Bulk, especially if you run Rain-Dish and some Rain Dance, is just outstanding. Leech-Seed, Scald, Giga Drain, and Substitute make him LAST FOREVER - plus, he handles enemy water-types. I know a lot of people don't consider him at all unless it's with Swift Swim in Rain, but he puts up one hell of a stall.
I used Lapras, but I'm biased. Please, use Shell Smash Cloyster. The only weaknesses you have to worry about as a whole are electric and grass; Cloyster gets hit by Fighting pretty rough, but Skill Link Icicle Spear and Rock Blast are really useful (Ludicolo and Slowbro invite a Bug weakness that Rock Blast covers, so it's more than just secondary Skill Link fun). Rapid Spin finishes him up. The ONLY reason to use Lapras instead is that it can learn Thunder(bolt if no rain), and Heal-Bell from Gen IV. Good, but not really key. I'll add Starmie here too, because I already mentioned Cloyster as a rapid spinner. Either one works, really; Starmie does out-speed Gengar ect, but I feel like Cloyster will catch them off-guard. Starmie also learns thunder(bolt), if that's really necessary. To be honest, I've never used Starmie, so I can't speak of it's pros or cons, besides that every time I've seen it used by others, I've seen it die pathetically.
Tentacruel and Jellicent are worth mentioning, too; great special defenders that compliment Slowbro and Vaporeon really well. These guys give you an absolutely solid defense, with nice, interesting typing.
Kingdra, Kabutops, and/or Carracosta are all pretty good sweepers, all similar but with their own virtues. Carracosta will rely mainly on Shell Smash like Cloyster, but the other two need rain support. Water is pretty neutral attack-wise, so the extra stab makes it threatening.
I don't know if this is really enough to make one, coherent team, but it has enough building blocks that there should totally be enough to make some teams with.
Mine ended up as Cursepert, Slowbro, Heal Bell Lapras, Shell Smash Carracosta, Wish Vaporeon, and Rain Dance Kingdra.
I know there are areas where it could be better, but it wasn't really designed for the competitive levels that are being looked for here, either. It does hold it's own though; a lot of teams aren't really designed to handle more than one Bulky Water if you can take their counter out quickly.