If you get sand in the seals, there is no need to remove the gasket from the groove. Simply rinse the sand or dirt off of the gasket with fresh water.

To put the gasket back into the groove, you should be able to push it in as far as possible with your fingers and then clamp the boat together one time to fully set the gasket into the groove. Be careful not to tear the gasket while putting into the groove. If you cannot get the gasket far enough into the groove to clamp the boat together you can use a nylon spline roller or the eraser end of a pencil to gently settle it into place enough to clamp the boat together.