Once you let go of the charge attack, you'll move forward automatically, and upon entering the water, the speed of the dash will carry over for several moments - letting you get to and from your ship quickly. To perform this correctly, you will either need to stand on a ledge (this can work either on a rock or cliff facing the ocean, or on the edge of your ship), or you can stand in the shallows just one step before you enter the water to swim. This is because the physics of the water allow any moving object to stay at the velocity and direction at which it enters for a period - when jumping into the water from the crow's nest, you'll shoot straight down. However, if you position yourself correctly, you can use it to move along the water at incredible speed for a good distance. The Sword Dash allows you to charge up and move a short distance forward quickly while dealing incredible damage - but after the dash you'll be stunned for several moments. You may know that holding down attack with your cutlass will charge up for a dash attack - but did you know it can used to slice through the water at incredible speed?