Apparatus for recovery of liquid hydrocarbon

A pump unit is described for recovery of liquid hydrocarbon from a body of liquid with a hydrocarbon/water interface, comprising a pump with a pump intake, and a linear probe, fixed in relation to said pump intake, and oriented to extend perpendicularly to said hydrocarbon/water interface and through said hydrocarbon/water interface, when in use, said probe including antenna means for generating an electromagnetic signal and electrical driving means for driving said antenna means, said driving means including signaling means for generating a signal indicative of the linear location of said hydrocarbon/water interface relative to said pump intake, wherein said linear probe includes a linearly extending electrically conductive member comprising said antenna means, a non-conductive coating on said conductive member, and means for electrically driving said conductive member with a low frequency electrical signal