How bad is it? It's one of the shoddier SyFy monster movies. That's an accomplishment of sorts, I guess.
Should you see it? No.
Swamp Shark and its main interest lies in the cast of former child actors: Tracey Gold, Edward Furlong, Bug Hall, etc. There's a lot of poorly conceived ideas, explosions without consequence, plot laziness, cheap work-arounds and just a general feeling of contempt for the audience. There is one good scene: the giant fire-breathing spider water skis!