You win at darts a second time and get a submarine ticket.
No. You only go down in the sub once, then bring your photo back to the pub, where it proves to be a movie prop.
Along the bottom, you will find a brightly-colored Nessie face and get a photo of it. Bring it back to the pub where it is revealed to be a movie prop.
Take the photo of the "loops in the water" back to Mews.
You don't. When you are in the submarine and find the Nessie "head", position the light on it and take a photo. Show it to the dart players at the pub.
The head monk won't give you the scalp, but he gives you a lantern. Go outside, climb above the monastery, to the upper left, and you will find a footprint in the snow. Take a photo to show to Mews.
You need a photo of Nessie at Loch Ness, a tooth from the Chupacabra from Puerto Rico, and egg shells from the nest of the Jersey Devil in New Jersey. (see related solution)
Take it back to Mews. Once you have gotten the photo of the Yeti footprint, and proved the other three cryptids (Nessie, chupacabra, and the Jersey Devil), Mews will send you to track down Bigfoot.
You have to look around the island is't simple
Dive to the bottom and go left, and there is a colorful Nessie head. Take the photo back to the pub.
When you get the submarine ticket at Loch Ness, dive to the bottom and then move forward. You should see a Nessie "head" sticking up. (If you look past it, you see it is a prop.) Take a photo and go back to the pub.
After you only get a footprint photo from the Himalayas, Mews decides that it is too difficult to track the Yeti. When you prove the other 3 cryptids, he sends you in search of Bigfoot, and you have to rescue the creature from the evil Gretchen Grimlock.
It means that there is scientific evidence that the cryptid exists, which is what you are trying to do for the 4 unproven cryptids. When all are confirmed except the Yeti (and you have the footprint photo), Mews will send you in pursuit of Bigfoot, who is soon confirmed.