The Sharknado films are nuts. This one isn't comparable (ie it isn't wilfully stupid and it's actually well made) but let's face it: Every shark film exists in the shadow of Jaws, and always will.

The attack at the start isn't graphic and it's fairly brief, but it definitely has impact. It isn't really a spoiler to warn people who might prefer to brace themselves, so I did it on this occasion. :)