[SauronOfMordor]

Fathometer. Low power, high frequency, short duration ping directed straight down.

Thanks, I get it now. So what the Navy investigators are implying is that, once he saw the fathometer readings did not jibe with his chart, he should have gone to dead slow and taken more readings (which may have shown him that the charts were out to lunch)

[fooman]

Best explanation I have seen that makes sense.

I still say he gets his pension and a gig teaching 'dont let this happen to you'