Certainly looks a very interesting machine,as long as it works and you are happy using it for that specific job then that is all that matters,i use a old Musketeer that i use for shallow river detecting in the UK,its mounted on a straight shaft using a tallman bottom rod and the control box that i wear around my neck.It gives me some vital extra depth and with the smaller 7.5'' coil i find that i dont get as much drag with the running water.
Only use it maybe upto 3ft of water looking for roman coins that have been thrown into the water as votive offering to the water gods.