What does the term "porpoising" indicate in relation to a boat's movement?

The term "porpoising" refers to a specific movement pattern of a boat where it alternates between rising and falling in a manner similar to how a porpoise behaves when it swims. When a boat's trim is set too high, it can cause the bow to lift excessively out of the water. This results in a situation where the hull may leave the water intermittently and then re-enter, creating a bouncy or up-and-down movement that disrupts the smoothness of the ride.

In this context, having the trim too high amplifies the porpoising effect, as the boat's stern may dig into the water and then launch back up, leading to instability and discomfort for passengers. A properly trimmed boat avoids this issue, allowing for stable and efficient movement through the water. This understanding is crucial for operators to adjust their boat's trim to maintain control and ensure a comfortable experience while on the water.