Worms, Eels and Sea Snakes, etc.

http://monstersandbeasts.blogspot.ca/2012/06/flat-worm-thing-prometheus.html,
http://www.youtube.com/watch?v=DNHx5GI1KQE,
http://tech.ca.msn.com/animal-imposters

http://en.wikipedia.org/wiki/Giant_moray Eel
Moray Eels Grab Prey With "Alien" Jaws
http://news.nationalgeographic.com/news/2007/09/070905-eel-jaw.html,
http://www.livescience.com/1834-eels-doom-prey-alien-jaws.html,
http://www.sciencedaily.com/releases/2007/09/070905134523.htm,
http://www.naturalhistorymag.com/biomechanics/04977/jaws-two

Engineered monsters that were never meant to be just kept in a lab.
http://www.avpgalaxy.net/alien-movies/prometheus/creatures ,
http://screenrant.com/prometheus-deleted-scenes-blu-ray ,
http://www.hollywoodreporter.com/news/ridley-scott-prometheus-alien-324981 ,
http://www.prometheus2-movie.com/pages.php?id=5 ,
http://avp.wikia.com/wiki/Trilobite ,
http://www.youtube.com/watch?v=jXvQNAkaNag

http://www.youtube.com/watch?v=EFEiT0erZIo ,
http://en.wikipedia.org/wiki/Hydrophiinae ,
http://www.telegraph.co.uk/earth/wildlife/9634277/Scientists-find-new-sea-snake-species-in-a-museum.html , 
http://blogs.discovermagazine.com/notrocketscience/2012/11/20/the-deadliest-sea-snake-is-actually-two-look-alike-species

http://paranormal-intersection.blogspot.ca/2012/05/river-monsters.html
River monsters, monsters in space & on other worlds.
H.R.G. sure knows how to design some monstrous things.
https://giger.com/gigerframeset.php, http://www.hrgigermuseum.com
Also see,
http://monsterfaces.weebly.com/creatures.html
for another perspective of monsters.

https://paranormal-intersection.blogspot.com/search?q=HRG

Ocean and River Monsters, etc.

http://www.diffen.com/difference/Octopus_vs_Squid,
http://www.youtube.com/watch?v=v_uU8PaqJ9g, http://www.youtube.com/watch?v=HdNAht0oYjQ

Although more mysterious than paranormal, these are certainly some of the most dangerous creatures in the world.
http://en.wikipedia.org/wiki/River_Monsters#Season_4:_2012,
http://www.youtube.com/watch?v=tfd5p1JqUsw,
http://animal.discovery.com/tv-shows/river-monsters,
http://www.youtube.com/watch?v=FMIN0XVKfPE,
https://www.facebook.com/RiverMonsters,
http://www.youtube.com/watch?v=LudndCm70lY

Lots of people like to eat things that are still alive.
http://www.youtube.com/watch?v=oNy8MUPOAtQ,
http://www.youtube.com/watch?v=-4RmkdAoQB0
And when various creatures are large or fast enough, they will eat people.
http://scifi.stackexchange.com/questions/18002/how-did-the-black-liquid-work-in-prometheus

http://tech.ca.msn.com/animal-imposters,
http://paranormal-intersection.blogspot.ca/2012/05/worms-eels-and-sea-snakes.html