Careful with the "depth is safe" assumption, sonobuoys can deploy both over and under the layer, and TASS/VDS sonar both listens under the layer in tandem with the ship's hull sonar and has no baffles blind zone.
So, ironically, if you are shadowing an advanced ASW unit, you are sometimes safer over the layer; since you can go in to his baffles only in that depth bracket.
By the way most of the soviet ASW ships in this scenario are NOT advanced so you are probably safer deep under, but you still have to worry about sonobuoys, also remember that where there is an active sonobuoy, almost always are plenty of passive ones you cannot see; so be very careful.
I don't know how realistic it is (perhaps a submariner in the forum can tell us), but I have found in numerous occasions that the only way to survive an intense air ASW search (the dreaded "blanket of sonobuoys") is going within the layer and keep it slow.
Of course you are mostly blind yourself (albeit if you are carrying a TASS you can still listen under the layer, and of course you can stop and go to periscope for some minutes every now and then) but for transit and evasion it has become my SOP, because I have found no other effective means of survival.