SAAMI put out 2 guides on dealing with guns and ammo that has been submerged in the water
Guidance on Firearms
http://www3.nssf.org/share/pdf/SAAMI-Guidance-On-Submerged-Firearms.pdf
Guidance on Ammunition
http://www3.nssf.org/share/pdf/SAAMI-Ammunition_Exposed_to_Water.pdf
From: SAAMI via Guns.com