Here is the photo of Gunslinger1's swim step.
My off the cuff assessment is that either there was a defect in the manufacture of the swim step, or the ladder has been stressed--like a 400 pounder jumping on it.
There appears to be cracking of the upper laminate--both at the stress load plate and the sides of the swim step. Also there is a small crack inboard and above the outboard plate. This tends to make me suspect that perhaps the laminate was thin on the surface.
Repair:--most likely there is core damage. I would pull the bolts for the ladder. Then asses the nature of the core damage. A moisture meter will probably read high on this surface--(only valid if the boat has not had moisture on the swim step for several days. Even after a heavy dew, a horizontal surface may read high.
You can over drill the holes to assess the nature of the core moisture. It will most likely be wet, and compromised. I don't know if it is plywood or balsa. In either case, I would rebuild it with either Coosa board or marine ply 3/4" thick. You will have to remove the core--this may be done easier from the underside. But considering the cracks on the surface, in this case I would rebuild from the top. Cut out the cored area, feather the side fiberglass. Set in the new core with epoxy Where the bolts go thru, make this solid glass or PVC lumber. cut in bloc or a circle. The other option is to over drill the. holes, and fill with epoxy--and then drill the holes. I would overlay with two layers of 1708 fiberglass cloth (this is 17 oz biaxial roving at+/- 45* axis with 3/4oz epoxy computable mat) and epoxy. I would add put one more layer of 6 Oz cloth to be sure it was well tied over the edges. The non skid on this can be obtained with cabosil thickened gel coat. I don't think it is worth trying to save the old surface--but some might take that route. If so you would have to feather in the edges as you bonded to the side of the step. (You have to do. a little of that with the 1708.). To get good gel coat bond on the step, you should wash the cured and faired surface, with soap and water, then lightly sand with 80 grit. Do a quick pass with a propane torch to "flame harden". Then Gel coat should adhere nicely.
Another option would be to fair the surface. Then use either glass micro beads or ground walnut (or similar) shells set in epoxy. Finally several coats of paint in "Hatteras White"--close enough to match the gel coat in the C Dory. I probably would use the latter approach. Silica sand is a bit more aggressive than I like, but is a possibility some would use.
