Stay underwater as much as possible , and get the snorkel with a RWR system.
this will give you the needed protection, planes don´t fly underwater.:hmm:

stay surfaced is suicide later in the war.

Mast mounted RWR or not, I just got stomped while snorkeling by an undetected aircraft off the Shetland's in November '44. Stay under water for crying out loud, Coastal Command will spoil your entire day given half a chance...
Good Hunting

Yes , it happens in real life, snorkels bombed or machineguned, but is better this than stay sufaced and try to dive.

Also raise some scope is recomended because it helps to detect incoming planes.

lol get the s-boot try to hit me at 40 knots!!!!