Buy a couple of "Big Job" patch kits or something similar at your local Ace Hardware store. The glue works well underwater, it's amazing stuff. Those kits include a piece of clear vinyl. Cut the vinyl so it's maybe 1-1/2" bigger than the cut you're patching, round the corners. Put the glue on the vinyl up top out of the water when you're 100% ready to make the dive. You don't say if it's in the shallow or deep end. You'll need to be pretty good at holding your breath and you'll need to be aggressive about this. The best way, of course, is with a scuba tank and a weight belt. Assuming you don't have these, you'll need to figure out a way to attach a weight to yourself or have someone up top actually hold you down with a vac pole/brush. Obviously, a communication system must be clear so you don't drown!
Patch one cut at a time, try to keep your patches as small as possible. The glue works well underwater and it works well after being applied and given a minute or so of stand time before being applied to the liner. Obviously, the liner surface must be as clean as possible, I usually am able to do this good enough with my fingers, cleaning it doesn't have to be a big production. If it's in the shallow end you'll be able to apply the patch and then use your bare feet to hold it in place and press the edges down, if not, you'll have to keep swimming up to catch and and swim back down to keep teasing those edges into place. After 4 or 5 minutes the glue will have set, after a few hours the patch will pretty well weld itself in place.
Try to avoid overlapping your patches, a patch on top of a patch is not good. If you try to patch all of the cuts with one patch, you'll really need to be able to stay down there and keep pressure on the patch and keep teasing the bubbles and wrinkles out of it and keep teasing the edges down until it sticks. Yes - you can take a tube of glue underwater with you and squeeze some under the edges where they're not sticking, but beware! Some (or much) of the glue will glob out and take off on you, there will be globules of glue floating up and around you, some may end up in your hair and who knows where. Practice is helpful, I've had plenty of it. I have scuba equipment, tho, and that makes a world of difference. You may have to call a pool pro. It's obviously critical this get fixed ASAP before the washout gets worse and turns into an entire liner job/retrowel.
