Could you use this with a cordless dremel to make modifications underwater on rocks that you cannot take out of the tank?
http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=225-01
http://www.dremel.com/en-us/AttachmentsAndAccessories/Pages/AttachmentsDetail.aspx?pid=225-01