Abstract: To facilitate construction of an hydraulic dam, a water fillable barrier has a tubular water fillable portion with a tongue projecting from one end. The tongued end of the barrier may abut the tubular sidewall of a second such water fillable barrier with the tongue wrapped around the second barrier and lashed to the first barrier. This arrangement allows the effective construction of a corner in an hydraulic dam. To extend the length of the dam, opposed ends of each of two end-to-end water fillable barriers may be overlapped within a sleeve. When the barriers are then filled with water, they foreshorten. This pulls the overlapping portions back in order to form a high pressure end-to-end abutment between the barriers.