Garmin GPSMap 556s - can the sounder be turned off?

[Dry_Doc]

Question as per the thread title.
We're trying to 'talk' to some submerged hydrophone receivers using an over-the-side hydrophone, and the sounder is creating a lot of unnecessary noise in the water.
I can't see an obvious way to turn off just the sounder and keep the plotter on.
Anyone know if this is possible?
Thanks!

[Gmw]

Depending on how accessible the harness is, you could always disconnect the spur cable for the sounder plug

[jeffstevens763@g]

Why not turn it off altogether