80's movie with huge nasty monster.?

not much to work with here I was like 8 or 9 but all I remember is this one part where this couple is having in a tent by the lake,it was daylight kind of rainy and gloomy,then this huge black monster ripped into the tent tore them to shreds and ate them.that's all I remember.It was again late 80's.real gory,it wasn't cheesy monster looked awesome,sort of like the creatures from aliens look except it was like twice the size of those.thanks again.