30. Giant Sea Spiders
While none of the sea spiders is poisonous to human beings or attacks them, they are creepy. Most sea spiders tend to be relatively small, but this is not the case with all. The giant versions of these spiders are usually found in colder waters, which is why Antarctica tends to be where they call home.
When the first photos of one circulated on the internet around 2013, many thought it was fake. Even Snopes claimed it was false. Since then, proven giant sea spiders have been found and even studied by universities here. Their studies found that spiders are able to breathe through their legs, allowing them to take in more oxygen. This, in turn, allows them to grow more.