Depends on how serious a sailor you are. Correct answer would be to fit new bottom or get new hull.
A solution that worked for me on a wooden hull and which you might want to consider -tho' not without consulting other more experienced mariners- was this :
Strip off the paint for an inch or more both sides of and beyond the crack.
Drill a SMALL hole through the hull at the ends of the crack - this should ease any stress and help stop it spreading.
Armed with some webbing and some marine epoxy - West System for example - lay the webbing over the crack and paint/roll on the epoxy. When cured/dry, varnish it, stand with hands on hips and say "that looks pretty good for a temporary solution", launch boat, jump in, and,if foot doesn't go through bottom, go sailing.
Bryan's advice is spot on. Just one small refinement. After drilling the very very small hole use a craft knife to chamfer edges of the split to make a very shallow "V" effect and then fill as suggested. Once rubbed down, faired and re-painted it shouldn't even show. Work in dry conditions.
Good luck - John
PS - if you post this again on the "Mirror Matters" forum you might get further help. I expect many won't have seen your message on the "Website issues" forum.