YERE, success with Basculin.
@ Choice Band
EVs: 8 HP / 252 Atk / 248 Spe
~ Aqua Jet
I initially started with this set - I figured that with Adaptability providing it a stronger Waterfall than Kabutops, then I can simply spam CB boosted Waterfalls or Aqua Jets on my Rain team. This was not the case, however - it still gets walled hard by Water resists. Banded Waterfall was powerful, but not powerful enough. I had SD Kabutops, too, and it sucked that Tangrowth would simply render both of these mons useless.
After talking to DittoCrow and hearing his praise of his LO Basculin, I decided to give it a spin, with a bit of a tweak to better serve my team.
@ Life Orb
EVs: 252 Atk / 8 SpA / 248 Spe
Naive Nature (+Spe, -SpD)
~ Aqua Jet
~ Ice Beam
LO Mixed Basculin definitely worked better. Although the brute force of its Rain-boosted Adapt Waterfall has been reduced, the flexibility in switching moves has proven far more useful. Being able to switch from Waterfall to Aqua Jet to finish off a fast prey after a kill is really pimpin. With this set, breaking walls has been much easier, as Basculin can now lure and 2HKO Tangrowth with Ice Beam, paving a path for SD Kabutops. The combination of Adaptability's immediate raw power combined with its deceptively fast 98 base Speed have made Basculin one mighty beast.
It does have its flaws, though. Unlike Kabutops and Feraligatr, its paltry bulk limits its switch-in opportunities. Even more vexing for me, was the inability to boost its Atk - sure its hitting slightly harder than Adamant Kabutops with Adaptability, but that's not enough in many cases. In this respect, Crawdaunt beats Basculin as an Adaptability Water-type. It's a shame that Basculin is forced to go Jolly to outrun Sigilyph, because Adamant's extra Atk boost would be very much welcome.
Note that I didn't go Max Speed, since I only wanted to outspeed Sigilyph.