Apparently, GoPro changed the Protune tonal curves the HD Hero 3+ uses when white balance is switched off from what they previously used for the HD Hero 3. It seems as if they now use separate tonal curves for the red, green, and blue channel, while for the HD Hero 3 the channels all used the same tonal curve. The unpleasant outcome of this is that raw HD Hero 3+ footage gets a massive tint. To this time, no satisfying set of effects and their parameters is know to deal with such footage in Kdenlive or other open video editing and grading tools. All experiments so far were unsatisfactory.
Albeit this tint problem is only seen when white balance is switched off, this is exactly the mode you want to shot in your underwater footage. Thus, GoPro without any real need mucked around with Protune, making it useless. GoPro's Studio software is nothing more than a bad joke: since when is grading done on raw footage before the footage has been cut and arranged? Whatever GoPro is, it needs to go pro as soon as possible, as breaking Protune is ridiculous.
Over here were I live, we have grades that go from «1» (best, «A» in some other countries) down to «6» (worst, «F» grade). It may be a sign that the HD Hero 3+ thus translates to a C+ grade. At best.
Unfortunately, GoPro still don't gives any useful information about how to deal with Protune. They simply point you to their pointless Windows and OS-X software. Seeing this openly customer-hostile I'm not the only one getting HD Hero 3 Black Edition cams while their prices dives, as the 3+ seems to rot in shop shelves.