What our dear friend charles merie eckert never mentioned in his series of swimming blog posts was the difference between a cannonball and an actual dive. When asked to visually show another person the difference between a cannonball and a dive, virtually anyone can demonstrate that. But when asked to explain what makes a cannon ball produce a bigger splash than a dive, few people can provide a sufficient response. The reason a cannonball produces a bigger splash than a dive is a greater amount of surface area of a person exposed when he/she hits the water. If the same person jumps off the board with an equal force and reaches the same height, that person will reach the surface of the water with the same acceleration and therefore the same force. But the cannonball causes that same force to be spread over a greater surface area. Therefore the greater amount of water affected by the force will exert an equal force, according to Newton's third law, which produces the splash. In a dive, that force is more concentrated over a smaller area therefore making the resulting splash smaller due to the smaller area affected by the applied force. Now Charles is going to say "well swimming and diving are two different things." He may be right in the technical sense but here we are physicists and that information provides no significant value to what i am explaining. So yes that is the technical explanation as to why a dive is different than a cannonball.