Communicated by E. MeisterWe present a complete proof of the existence and uniqueness of solutions of a mixed boundary value problem for the homogeneous Laplace equation in an unbounded parallel strip based on the principle of limiting absorption 1. Introduction and statement of the problem 1.1. The floating body problem is a boundary value problem concerned with determining the surface waves produced by a vertically oscillating body floating in an inviscid incompressible fluid of finite depth with a free surface extending to infinity. This problem was introduced by John [13, 141.If one wants to find approximate numerical solutions, it is a good idea to split the problem in an inner and an exterior problem (cf.[17]). The further procedure is as follows. Find the solution operator of the exterior problem and show by the boundedness of this operator, that the Neumann data of the (exterior) solution on the cut section depend continuously on the given Dirichlet data. This allows to formulate an inner problem on a bounded domain with non-local boundary conditions on the cut section, which is equivalent to the floating body problem in the infinite strip. Now there are several possibilities to discretize this localized problem, cf., for example, the localized finite element method studied by Lenoir and Tounsi [17].Because of this Lenoir and Tounsi remarked in their paper, that the existence of the solution operator for the exterior problem and its boundedness follow by the uniqueness proof given by John [14] and by the principle of limiting absorption worked out in Lenoir and Martin [16].Martin and Ursell [9]. Therefore, their argumentation to construct solutions by the limiting absorption principle breaks down. Thus, in the present paper we go back and study the existence and uniqueness of solutions of the exterior problem. 1.2. Let us denote by x = (xl, x2) the elements in the two-dimensional Euclidean space W2. Let R, := W ' x ( -h, 0) (h E W') be an undisturbed fluid domain with the bottom surface B, := R' x { -h } , the free fluid surface F , := W+ x (0) and the left boundary Co := (0) x (h, 0). The domain R, represents one-half of the exterior domain in the problem of the floating body ( cf. [2,4-7, 13, 14, 16, 171). For R E W ' we define the cut off sets RR :Then the exterior problem of the floating body problem is formulated as follows. Problem A (Classical formulation). For each x E C1(Co) and 1 E C find all u E C'(i2,) n C'(Si,) such that 0 on B , lu on F , , u = x o n & , Au = 0 in R,, a,u = where a, denotes the outer normal derivative to the domain 0,. In the case of x = 0 we call it homogeneous and inhomogeneous in the other case.1.3. We organize the paper as follows: First we put Problem A in a Hilbert space setting and show in section 2 unique solvability for 1 E @\R'. For 1 E W ' the Hilbert space methods fail. Therefore, we give a Frechet space formulation of Problem A in section 3.In the rest of the paper we prove that this Frechet space problem has, for 1 E W ' , a unique solution under the assumption...