Has the mere premise of a movie ever totally baffled you?

The example: Shark Night 3d comes out today in theaters. The basic premise as I understand it is a group of college aged/high school aged friends go to an island in a lake with a cabin house… get drunk, have sex, party, yada yada… When somehow a shark (or multiple sharks, I dunno) get into the lake and the friends start getting killed by the sharks.

Well the seemingly simple option to me was….. why not stay on the island? Did the sharks grow legs?

Has a conundrum such as this ever happened to you?