I am working on a project and I am very very new to antenna theory, im used to Op-amps(Diff, filters, etc....) but this is new to me. I need to pick up a electric field 1mV/cm that can be produced up to 2 meters underwater. So 12.5mV at the source and 1mV, 2 meters away(if I converted it correctly, since it's a dipole the electric field created by the source doesn't propagate, inverse of the distance cubed). If I understand the theory correctly I have to make a antenna that resonates with this frequency, and from the looks of it it'll be a untuned antenna, correct? And also if the water's conductivity is low, this means the dipole will be larger. Im having trouble figuring out what shape and length to use. I looked up a dipole antenna but making a dipole antenna is impractical (1,600 ft long). If someone could point me in the right direction of tell me the kind of shape that'd be great.

 

Could find the edit, button. But I looked up and was thinking a loop might work, but it is directional. Or a double loop that's more Omni directional with a small wire gauge. And waterproof it. Any thoughts?