[SabreHawk]

Thanks Wiesia, an interesting read. Yes im sure it was done, but very little due to the risk involved and given the limited info on the seabed at any given location.
I'd think that in the 30's and 40's very little exploration of the sea bottom was done yet, only soundings for the most part. Which can produce depths and contour info but I doubt the type of soil and vegetation could be determined. But I could be wrong.

It certainly has to be risky at any rate, given that one cannot see where one is going and what is directly below other than pinging for depth under the keel.

Something else I've always wondered about was the use of the cable cutter on the bows of the earlier boats and exactly how this is done without getting tangled in a net.