The sharks weak spot is the nose. Improved answer: A sharks weak spot really depends on the shark itself, mainly the gills, eyes, and where its vast array of electrical sensors are located (on the snout)
Alot of them use a sonar-like sensors that emit soundwaves to help them "see".
IR sensors
Exploratory robots use motion, heat, and camera sensors.
the fork on the left
well it is what your pee is made out of and Sharks use it to mark their territory
buy
All snakes use heat sensors, they use them to find food, a shelter and what things are.
sharks cannot sneeze. since sharks live in waterthey use their nose (irnot their eyes) to sence and catch prey. a sharks nose is equiped toopen and close at will when not in use.
they are called: Ampullae of Lorenzini. These clusters of sensors are connected to small jelly like tubes through pores on the skin. Jeff Shaw Oceanic Defense http://www.facebook.com/OceanicDefense
The same sensors Air France uses on theirs.
The sharks that have barbels are generally nurse sharks and sharks that stay near the bottom of coral reefs as they are filter feeders and use them to scoop in plankton.