Absolutely, if you lost control of the sub, you have to accept that it is lost.
Anybody who jumps into, or falls through thin ice, into 4 gegree water is as good as dead ! Even if you came out, you will be frozen in minutes. Believe me, I spent my first year in Canada in Thunder Bay ( a.k.a. Port Arthur and Fort Williams), which has cold days of -35 degree fahrenhite and I know how dangerous cold is and it requires respect [:@].