We have adapted EM sensors developped for spatial to airborne and marine geophysical exploration.
First application was sea Ice thickness measurement with for Alfred Wegener Institut
Geophysical Electromagnetic method is an unique tool to measure the electrical property (conductivity) of basement.
Already used on marine for reservoir appraisal (ref. EMGS) and for buried pipeline; interest is growing for underwater mineral resources mapping specially for SMS deposits. Such target is deep and relatively small size (hundred meters).
Tools and operation method have to be developed . ROVs or AUVs would deployed one or several sensors, at low elevation or on the sea bed. Frequencies range of such exploration are upper than CSEM deeper sounding, instrument size can then be reduced to offer a different operational mode.