It's been suggested that it was targeted at a general audience, but I think the problem was a lack of a specific target at all.
As a result, there was not enough diving for the divers and extreme sports types and not enough detail or diving induced drama to interest either of them.
There was ample opportunity to go into techical details to attract the science and technology types, but the most you ever got was a too second look at unexplained equipment. Unless you were a technical diver, that brief exposure was lost on you already.
The history buffs were a possible target, but I suspect they were not impressed as there was very little history covered in anything more than a very elementary level. And the premis that they were "solving" mysteries was pretty hokey, as the work had long been done by someone else. And as indicated above the endelss repetition got old and left you withe the feeling they were filling the available time.
In my opinion, the show would have been better received by more people if it had stuck to it's unique aspects - technical diving in often deep and challenging conditions with very interesting and often high tech equipment.
It could have focused on underwater and on deck footage and tried to capture and convey the feel of technical diving. That would have appealed to the extreme sport crowd, to anyone who liked a little drama and to the science types as well. And you could have reinforced the science/techology side a bit by added a mini-feature in the middle of each show with an equipment review or interview with a manufacturer in a "how it'd made kind of style". That would have also been popular with the divers who would watch it anyway.
Maybe someone else will pick it up on the sports channel, science channel etc with a little more focus.