Fix only the crack.
You need to remove all the damaged fiberglass from the crack.
Sand off all the gelcoat or paint from around the crack.
Then fill the resulting hole with multiple layers of fiberglass and resin.
This should be done from both inside the hull and out.
Otherwise there's a good chance the crack will return.
After hardening, sand smooth, then paint.
Instruction videos for fiberglass hull repair are available for free on line.
I'd worry about whats under the false floor too! Could be rotting stringers, or water soaked foam.....which would severely limit the "seaworthyness". Would be a good idea to post a few pictures of the rig and the damage.
If there is foam under the floor and you filled the boat with water then the foam is soaked and needs replacing. Depending on how long it has been leaking and the layout of the grid under the floor all the foam may be wet.
If you filled the inside of the boat with water, how did the water make its way to the hull? Crack in the floor as well?
Pictures of the boat and location of the crack would definately be helpful.