Yes, I know where to click to make it louder.

But anytime I go back to my hydrophone I fell unsure if it's as loud as it could be and click it again just to be sure. I thought a kind of mark could be added to the knob, like on these knobs for adjusting volume of speech, effects etc. in game settings.
Or maybe it could be set at max volume as a default by changing proper value in some config file?
Thanks for answers, Mates.