Method for identifying subsurface features from marine transient controlled source electromagnetic surveys

A method for evaluating features in the Earth's subsurface below the bottom of a body of water, comprising:

• applying at least one of a controlled source, transient magnetic field and a controlled source, transient electric field to formations from a position proximate the bottom of the body of water;
• detecting at least one of an electric field amplitude and a magnetic field amplitude from a position proximate the bottom of the body of water, the detecting referenced with respect to a time at which a current source used to apply the at least one of an electric and magnetic fields is switched;
• and
• inferring the presence of a feature in the subsurface from the measurements of the at least one of the electric field and the magnetic field, wherein the measuring and detecting is performed such that a ratio of the depth of the body of water to a depth within the subsurface below the water bottom of the feature is less than about 1.5.