I have done a search on this and can't find any explination. I would think that to much water would cause the gourd to rot and split open. Was the gourd still green and on the vine or was it in the proccess of drying? I have seen gourd sites offering cracked gourds at a discount so apparently it is something that happens.
I did see some information on repairing cracked gourds though. You may try glueing it back together if it was in the proccess of drying.

Excess water can cause gourds to take in too much and split. I would just hold off and wait. Sometimes if the split isn't too deep they will heal and eventually dry and cure OK. If it's real deep there isn't much you can do. I've had a couple this year grow into a chain link fence supporting them. When I found them, the wire had cut into them deep and brown juice was running out. I cut the wire and left them go and they sealed themselves and kept on growing. It left some deep scars but the gourds appear OK. If they dry and cure OK, you can always use the section of gourds that are alright to craft into other gourds. Gene