The Phylum Cnidaria are very interesting. They are free swimming marine animals. Jelly fish have so many neat features about them such as there tentacles that can sting, the ability to function without a brain and also the way they move. They are very interesting to observe. They aren't opaque so you can see through them and look and all the neat features. They have long tentacles they move in a jet propulsion motion.http://ataillah.tripod.com/jellyfish.htm

Arthropods

http://163.16.28.248/bio/activelearner/29/ch29c1.html
3 characteristics of arthropods include an exo skeleton, segmented body and joined legs.
The reason i chose this arthropod is because when i went to Arizona in 2012, i got to see a bunch of scorpions fight each other and it was a pretty cool sight to see because where do you get to see that. Scorpions also are very interesting to look at.

Squid parts

https://www.google.ca/search?q=squid+diagram&client=safari&hl=en&source=lnms&tbm=isch&sa=X&ei=_Z2PUqTLI5TmoASxiICwDA&ved=0CAkQ_AUoAA&biw=768&bih=928#facrc=_&imgrc=Ih3QSgXMp-dRfM%3A%3BXqwicqlcgVVV1M%3Bhttp%253A%252F%252Fwww.exploringnature.org%252Fgraphics%252Fmollusks%252Fsquid_diagram_color72.jpg%3Bhttp%253A%252F%252Fwww.exploringnature.org%252Fdb%252Fdetail.php%253FdbID%253D43%2526detID%253D2796%3B792%3B61

The thing i found most interesting about this animal is the fact that is has so many amazing functions like the siphon that shoots water out and the chromatophores lets the squid change colour. The other cool thing i found interesting is the fact that the ink sac can actually be used to write with pencil. This  animal is useful to the environment because squid love cold fresh water and if there is squid, then you know the water is fresh! They also are apart of the food chain with whales such as the sperm whale.