De-ballasting
To remove the water ballast while in the water, I've used a small garden hose pump with a power drill. Mainly, I do this to get the salt water ballast out. I prefer to keep the tank filled with fresh water vice salt water. The boat tends to get very sloppy when there's no water ballast in the tank. I'm not sure why you'd want to do it underway. You won't gain any speed since this is not a planing hull design.Anyway, that's my method of de-ballasting.Tom