Could 1980 sonobuoys listen below the thermocline?

Could sonobuoys in 1980 be set to listen below the acoustic layer?

Some could lower a hydrophone beneath the layer in theory, but the equipment was unreliable and easily lost, so the period system relied more heavily on SOSUS below the layer and sonobuoys above it.

The exchange separates the floating sonobuoy body from the hydrophone it lowers into the water. Period equipment could attempt to listen below the layer, but it did not do so reliably and had a habit of getting lost. Modern sonobuoys handle that task more effectively, which makes present-day examples a poor guide to the scenario. In the 1980 sensor picture, SOSUS is strongest below the layer while aircraft concentrate many sonobuoys above it.