So for a while now I've been mildly annoyed that UB Fish was just worse than UW Fish due to the lack of good maiindeck answers to DSC, not to mention the whole 'WTF MATE' of not having Jotun Grunt. Eventually I gave up on that and decided just to splash for the best 2 cards black had to offer and came up with this.
//NAME: Super Fish!
// Lands (19)
4 Wasteland
1 Strip Mine
3 Tundra
2 Underground Sea
1 Island
1 Plains
4 Flooded Strand
3 Polluted Delta
// Mana (2)
1 Black Lotus
1 Mox Pearl
// Counters (4)
4 Force of Will
// Disruption (12)
4 Null Rod
3 Stifle
3 Duress
2 Swords to Plowshares
// Other (6)
1 Time Walk
1 Ancestral Recall
4 Brainstorm
// Creatures (17)
2 Azorius Guildmage (Previously 2 Daze)
3 Jotun Grunt
4 Dark Confidant
4 Meddling Mage
2 Savannah Lions
2 Isamaru, Hound of Konda
// SB
SB: 4 Tormod's Crypt
SB: 3 Orim's Chant
SB: 3 Eight-and-a-Half-Tails
SB: 3 Umezawa's Jitte
SB: 1 Swords to Plowshares
SB: 1 Duress (Could be 4th Chant or Tundra as well)
All of the card choices are pretty obvious, so I'll just give basic reasoning behind the deck.
I wanted a version that maximized the mana denial theme, hence the 4 Stifle in addition to strips and rod. Duress was also superior to just about any secondary blue counter I wanted to play in the Drain or Combo matches. The mana base looks a little silly, but it was created on the same principles as BDW was in Extended, maximize mana options and always have double colors available in a pinch. I kind of want the 8th fetchland, but I can't figure out what to cut. :SadPanda:

My post-board plan against opposing combo is pretty simple, bring in Orim's Chant and make them try to fight through infinite bullshit to actually win the game.
I'm actually most happy with the Fish mirror. Not only do I draw more cards than them usually, but Guildmage is the best maindeck tool I have to beat them in a long game. Post-board I've completely ignored the 'steal threats' or 'kill the other guy' plan and simply chose cards that completely invalidate my opponents deck. 8 1/2 Tails means I get to cheat in all fights, my men don't die to plow and I can make stuff like Threads and opposing Jitte fall off other creatures if I need too. Meanwhile I run my own set of Jitte, as it's by far the best card to have active in the aggro match.
Generally this deck shares many of UW's matches, but gains a slightly higher edge in Drain and combo matches by having better options. The one major match I totally skimped on was Stax and it shows. Honestly if I actually had reason to care about the match, I'd board 4 Kataki, but I don't. if your metagame is different, I suggest you make that change and find room for the 8th fetchland.
I've been kicking the deck around for a while now, but I have nowhere to play it until summer. So enjoy.
EDIT: Fixed my stupid fucking typoing lying list.