The only thing I can think of (and it may/may not work) is to edit your save game files.
Go to \Documents\SH5\data\cfg\SaveGames and there you will find your save games. Now you need to figure out which of the folders there is your save game in question. Once you figure that out open up ActiveUserPlayerUnits.upc with Notepad. Find this section:
[UserPlayerUnit 1]
ID=VIIC
NameDisplayable=Type VIIC U-boat
UnitName=U021
UpgradeClass=2
Type=VIIC
UnitInterval=1940-07-30 00:00:00, 1945-12-31 00:00:00
ExternalClassName=SSTypeVIIC
Nationality=German
Evolution=Normal
Damage=0.520000
CO2Level=0.000000
TextureName=NULL
LightmapTextureName=NULL
NormalmapTextureName=NULL
MenuSilhouetteTextureName=Typ_9_1.tga
MaxOfficers=6
MaxPettyOfficers=32
IsUnderwater=false
StartUserPlayerUnitMissionDateTime=1942-09-20 15:00:00
CurrentUserPlayerUnitMissionDateTime=1942-09-20 15:00:00
SilentState=false
Change the Damage=x to Damage=0.0
Once again may or may not work. Let me know either way
