Nate Hoyt
Member
Go to Lowe's or Home Depot and peruse the concrete anchor selection. There are a lot of options, they are fairly cheap, and none require epoxy/adhesives. What you are trying to do is common, albeit with concrete, not granite. Red Head has wedge anchor and sleeve anchor options that tighten by wrench that would be perfect (they have drive-in options also like I mentioned previously, but I think they'd be a headache underwater). A waterproof drill, a lump hammer to seat the anchor in the hole, tabbed d-rings to connect to, and a ratcheting box-end wrench to tighten until the wedge bites and you'd be good to go.
Nate
Nate