I've built several ponds over the years but I have a unique situation this time. I am currently constructing two ponds on either side of my sidewalk. The water level I am needing will put it approximately in the middle of the thickness of the slab. If I remove the section of sidewalk then connecting is no problem as the liner will be one piece. This would require a bridge which I would prefer not to do. Does anyone know of a (for the lack of a better word) tube or pipe that I could use to connect the two sides and maintain a watertight seal between the two sides. This way I could tunnel under and leave the sidewalk untouched. The tube or pipe would have to be big enough to allow fish to travel from one side to the other.