Abstract: A collar for repairing a marine support has a tubular upper segment, a tubular lower segment, and a middle segment providing a transition region between the upper and lower segments. The collar can be opened and closed along a slit extending from the upper end of the collar to the lower end of the collar. To repair a marine support, the collar is opened and positioned so as to surround the marine pile and the extension. The collar is then closed and secured along the slit. The upper end of the collar is secured to the extension, and the lower end of the collar is secured closely along the perimeter of the pile. A flowable fill material is then injected into spaces between the collar and the marine support, filling or encasing voids or damaged areas on the marine support.