I've played the Soggy Brains deck a few more times since its first outing. To this point it's winning almost exactly half the time.
A couple of the match losses were to Eldrazi decks, which are a pretty tough matchup. I've had losses to both an aggro Eldrazi deck and a ramp version. The aggro version was running creatures like Thought-Knot Seer and Reality Smasher that are really tough to handle in a delay deck like Soggy Brains. Worse, it had Stratus Dancer to counter my Engulf the Shore. The ramp Eldrazi was pretty happy with all my delay tactics, since that just gave it a chance to ramp up to Ulamog, The Ceaseless Hunger and exile my Brain in a Jar and/or lands. I felt a lot better about that matchup once I sideboarded in some counterspells, but didn't get a great draw and lost the second game anyway.
Another loss was to a super-fast Elf deck, which just dumped about half a dozen Elves into play on the first 3-4 turns and then finished the job with Shaman of the Pack. Not much a blue deck can do about that short of countering the Shaman or bouncing all the other Elves when it's played, but my draw didn't support either option. That Elf deck has all kinds of trouble against other control decks, though, so I doubt it will show up too often.
And then there were the losses due to pilot error. Two of those stand out, both against mostly-red aggro decks. In one case, I chose to cast Engulf the Shore to bounce my opponent's creatures before he actually declared his attackers, which gave him opportunity to activate a Needle Spires and hit me for four. That one hit turned out to be the difference when he was able to just barely finish me off just before I got the zombies and Part the Waterveil out for the win. In the other case, my deck was refusing to turn up Rise from the Tides, but I had three Part the Waterveil and a ton of mana. So I used the awaken cost to make a 6/6 land and attacked with it for three turns...which adds up to 18 damage, not 20. Basic math fail. Would have won that if I'd just used the awaken option twice, which I could afford, but just didn't think about. Those losses are frustrating, but good learning experiences.
This isn't the only deck running around with waterlogged zombies. Another mono-blue version without the Brain in a Jar and a blue-black version with the Brain were played at Grand Prix Manchester. I'd considered the blue-black version myself, but without cards like Languish and Dark Petition it's not really feasible. Maybe if I find someone willing to trade them someday. Anyway, it's nice to see that the zombies-from-the-surf concoction has some viability even at high levels of competition.