doesn't look so bad to me
most important thing is to do some kind of repair before sailing again

if i were you i'd dry it out thouroughly, maybe use a heat gun on low, or good sunshine
clean it up as much as possible with acetone, the solvent for uncured polyester resin
pick out as much debris from the crack as possible
cut of a small strip of glass fibers and then pull a few threads from the ends
mix up the smallest amount of polyester resin you can, for me that's 100mls as my catalyst dropper's minimum is 1ml
paint the mixed resin over the bare area and then using a toothpick stuff as manny glass threads as you can into the crack
take time to keep brushing on resin carefully so the threads all get soaked
when crack full and threads sticking out continue brushing thick coats of resin onto bare area while trying not to pull threads out of crack with brush
leave it alone overnight
next day it should be hard enough to cut the long fibers off and then grind down to just raised
if crack not fully filled, repeat until filled
finish off with another thick coat of polyester resin, but don't try to make it so thick that it runs down the hull, you just want it to puddle on top, (easy to do on a nacra base maybe harder on the hobie knife edge)
when you have a good thick cured layer of resin over all the fibers smooth it all out with a big file but don't file it all off
ago over it with 2 or 3 coats of white gelcoat and then you should be good
if you' got your temp/catalyst mix right
stuff as many of those threads that you could into the crack