So for the past few months I've been away from KSP since I couldn't get version 1.1.2 to run. This was because of an unsolvable crash when the scene changed from the main menu to the space centre.
Recently I downloaded KSP onto my desktop computer (Win 10) with the expectation that since it was newer, it would work. And it did once I ran it as the administrator.
Then I tried to make it work again on my old 2012 macbook pro (retina) and found that the solution was specifically linked to the "underwater FX" apparently this one graphics option was so greedy for hardware space that it caused a crash every time.
I'm posting this in case anyone else has the same problem. Apologies in advance if this is the wrong forum space for this kind of post