With all due respect, it seems to me that if I'm in fog or darkness and the radar shows a potential collision situation on the screen I am going to stop what ever else I'm paying attention to and dedicate myself to that situation. That being the case, as a part time fisherman and guy who just spent too much $ on a new to me boat, I don't think I'm going to spring for a MARPA, capable radar setup. At the risk of sounding like someone who knows more than they do( which is certainly not me cause I will admit I don't know sh#*t) I think it's possible that sea sense, caution and a prudent awareness of one's limitations might be the best tools we have to avoid bad things happening in our boat.