Or could be just a giant river otter... Orrrrr maybe a pitbull in a life vest with a dorsal fin
Click on video
http://vid257.photobucket.com/album...2-7EAC-4136-943A-4C035742BAE4_zpstuwjg3s1.mp4
Click on video
http://vid257.photobucket.com/album...2-7EAC-4136-943A-4C035742BAE4_zpstuwjg3s1.mp4