Sounds like a big Thresher to me, with that big of a distance from dorsal to caudal(assuming distance from top of dorsal to top of caudal). If it was 8' form base of dorsal to base of caudal that would be a serious monster

Like a GIANT Mako. Not too likely since the biggest confirmed Mako was something like 13'.
I just saw a BIG brown shark come check me out the other day, dorsal finning and all. Probably 8'-10' seven gill. It was a sight to see for sure.