At the moment, GoPro's new HD HERO2 (350€) is my #1 candidate. Some of the underwater clips I've seen so far on YouTube look quite decent and IMO better than ones taken with an old HERO or some other competing products. That is, if a third party solution is used for underwater footage, thus requiring an additional investment, besides the optional LCD BacPac (100€) needed for compositional framing.
Price-wise ActionPro's SD20F (269€) is without a doubt a much better deal, it coming with a clip-on LCD module, laser pointer, remote control and waterproof case (cam w/o LCD, -20m), with an optional SCUBA housing (cam + LCD, -40m, 30€) available as cheap accessory. Spec-wise it seems to be equivalent to GoPro's previous HERO.
Another interesting alternative is ACME's new CamOne infinity (249€), with built-in LCD and supposedly exchangeable & manually re-focusable optics. Unfortunately, though coming with a waterproof DiveBox, there's no practical SCUBA ready underwater solution yet.
GoPro's main advantage in my case is the availability of several practice-proven underwater solutions like BlurFix's flat lens port (with interchangeable 55mm filters, 80€), Subspace Pictures' adapted housing with dome port (for a true undistorted 127° FOV, 252 CHF), UK-Germany's flat lens aluminum housing (rated to -100m, 499€) and Eye Of Mine's flat lens double-housing (for stereoscopic 3D, 190€).
With a bit of luck I might actually get a closer look at some of these options at the boot 2012 fair in Düsseldorf end of this month, which I intend to visit in order to gear up for my next venture into darkness.
