A friend asked me if I've done much study in cryptozoology or Fortean topics. If so, were there any cryptids or anomalous phenomena I found particularly compelling?
We need to draw an initial distinction. Some cryptids, if they exist, are biological organisms. Therefore, assessing reported sightings depends in part on what's naturally possible or probable.
Conversely, some cryptids, if they exist, are numinous beings. So naturalistic criteria don't apply.
Kraken
That may have its basis in the giant squid
Giant anacondas
It's possible that there are larger anacondas in the wild than we've discovered. However, beyond a certain length, an anaconda would have the girth of a subway train. How realistic is that?
Loch Ness monster
Several issues:
i) I guess the theory is that after the ice age receded, it left behind a geographically isolated species. Old glacial fiords. I don't think there's anything antecedently improbable about that.
ii) One issue is how many breeding pairs would need to reside in Loch Ness to maintain a replacement rate. You'd expect more sightings if there are more specimens.
iii) I believe Loch Ness has been probed by sonar beams, but nothing turned up.
iv) To me, the famous grainy 1934 photograph looks like a bathtub toy for kids (e.g. rubber ducky). And the picture has no frame of comparison to judge the scale of the object.
I'm guessing the Loch Ness monster is a legend, perhaps to promote tourism.
Bigfoot
i) If it exists, what is it? Is it an Old World ape that migrated to the New World across the Bering Land Bridge during the ice age? Or is it supposed to be humanoid (e.g. Neanderthal)?
ii) If it has humanoid intelligence, I'd expect it to produce corresponding material culture (e.g. Neolithic). That would be easy to detect.
iii) To my eyes, the famous Patterson–Gimlin film looks like a man in a monkey suit. Like those low-budget sci-fi flicks from the 50s.
iv) I've read about Indian tales of Bigfoot. But in Indian tales, Bigfoot is a numinous being. So that either rules out naturalistic explanations or else Indian tales reflect legendary embellishment.
v) A difficulty with Indian stories is establishing their indigenous pedigree. Since most tribes were oral cultures, it's hard to say how old the stories are.
And that raises the question of whether Indian stories have evolved due to contact with the white man. Could these be hybrid stories that reflect cross-pollination between Indian folklore and European folklore?
vi) I'd add that (iv-v) also apply to wendigo.
vii) I don't have an informed opinion about the Yeti. Perhaps such an animal could exist in the remote religions of the Hindu-Kush without scientific confirmation. Or maybe it's a tall tale for gullible tourists.
Chupacabra
From what I've read, this was first reported in 1995. That would be pretty inexplicable on either naturalistic or supernatural grounds.
Hellhound
I actually read a reported example of that recently Forget where.
In general, I believe that Old-Hag syndrome probably has an infernal source. I believe that individuals and cultures that practice witchcraft and necromancy can expect to encounter evils spirits, whether demonic or vengeful apparitions of the damned.
In her book, The Hands Feel It, academic anthropologist Edith Turner talks about specters and other spooky phenomena reported by locals at an Eskimo fishing village where she lived for a year. The village was located on old Indian burial grounds. Some of the graves were Eskimo witchdoctors.
Some of the villagers were Christian while others continued to practice indigenous witchcraft. Under the circumstances, I find it plausible that spooky things happened.