Sure you can, exactly as I stated. Load the sketch in to Fritzing. In the temp parts bin you find the part for the water sensor (because it isn’t in core parts.)
right click on the part in the temp parts bin and select export part
That will prompt you for a file name for the part (its title by default) and a directory to store the part in. You can then load the resulting part file as described to put it in the mine parts bin. You can also just move the part from the temp parts bin to the mine parts bin if you wish. A google search of the form “fritzing part water level sensor” then select images indicates the part is also available from this site:
Peter