Furuno FCV620 Fishfinder, Dual Frequency 50 200 kHz , 5 6' Color LCD Display HIGH

[@jojinapigkit4680]

you mentioned 50 and 200 kiloherzt as to deep and shallow water, now how deep and how shallow should we use 50 and 200 khz? you/furuno always mention it, 50 for deep, 200 for shallow, how will you define shallow and deep? where do we stand? thank you. please reply.