A line source underwater transducer may be used in conjunction with a parabolic cylinder reflector to produce a highly directive sound ray similar to that obtained from a shaded plane source. Poor patterns result from the construction of a unit where the element is at the focus of a parabolic cylinder reflector because the finite size of the element is so great as to block a large proportion of the reflected sound rays. To circumvent this difficulty an ideal surface is derived which will allow placing the line source out of the direct path of the reflected rays. This derivation and the construction and acoustic characteristic of the consequent transducer are discussed.