In a graph of acceleration versus net force, the slope of the graph represents the inverse of the mass of the boat. This is because according to Newton's second law of motion, \( F = ma \), where \( F \) is the net force, \( m \) is the mass, and \( a \) is the acceleration. Rearranging this gives \( a = \frac{F}{m} \), indicating that acceleration is directly proportional to force and inversely proportional to mass. Therefore, the correct response is:
the inverse of the mass of the boat.