I wouldn't lump all three of those together. I have seen next to no evidence of Nessie, a little more of BF but not much, but I've seen tons of evidence for UFOs. By definition they represent some sort of science that we can't explain. There's also a ton of evidence that the gov't is covering this up for some reason. Any time the gov't tries to cover something up, my interest increases
Take Roswell for example. Trained observers, not laymen, can attest that the crash debri was not from a surveillance or weather balloon, yet that's the story our gov't is feeding us. Our gov't is also telling us that the "aliens" noticed by observers were actually crash dummies. Why would we be dropping crash dummies from surveillance balloons? Why would they order kids' coffins for the crash dummies? Lots of unanswered questions here. Until they get answered I'm keeping an open mind.