bikedaft
Well-Known Member
Cement is significantly denser than seawater so for near surface holes some form work rising upto the waterline would allow the head of cement to stop the water flow. Chicken wire, rags, wood, paper shredded etc can all be used as bridging agents mixed into the slurry to bridge the hole.
I should also add that salt is an accelerator and will speed up setting time, sugar is a retarder and will slow down or even stop setting.
thanks
the boat in the OP was filling up their centre board case by the sound of it, ie "shuttering" in place already