Evening shipmates.
I have two thoughts on this.
1) I use wilhelms etc v7 no problems
2) I can save and reload without problems anywhere ie. 100 meters from land, submerged, underneath an enemy vessel.
I had the save submerged bug and dreaded CTD, this is what cured it for me.
Change the folder attributes for (assuming you are using the default dir) Ubisoft/SH3/xxx
Right click the Ubi dir ( If you have more than one game in your ubi dir, just check SH3 props) and remove the check from the read only box apply and agree to allow changes to all folders within SH3. Now ok. Try a reload from a previous save, before the problem save. When the game loads make another save and try load that. If your properties change hasn't taken, look here;
http://support.microsoft.com/kb/326549
Hope this helps shipmates.
Best regards.
Fubar2Niner