First post here, so apologies if I don't know all the etiquette.
LIDAR has been used to survey seabeds for a good few years now, I applied for a job with one of the Aussie companies.
From the descriptions above, you could use LIDAR to detect submarines by detecting "targets" that are under the water but not on the sea bottom, but for that you would need a three dimensional model of the area under the water that would allow you to compare "now" with "then", which would take a lot of computing time.
The second image seems to be a system for "reading" the waves to detect noise made by submarines, but this would be very noisy in terms of picking out any weak audio signals from the general background noise.
Sounds great, but you would be better off with a dipping passive sonar