In this paper, we propose a new scheme of transmission and reception of OFDM ( Orthogonal Frequency Division Multiplexing) signals for underwater wireless communications. The transmitter makes use of a kind of superimposed pilot signals, which are used by the receiver for estimating both the channel parameters (paths gain and delay) and the Doppler. Then, the estimated parameters are used for estimating the informative symbols in the zero forcing (ZF) sense. A new estimation scheme based on the resolution of two harmonic retrieval problems is proposed. Unlike standard methods, data resampling and estimation of residual carrier frequency offset are avoided. The efficiency of the proposed scheme is evaluated by means of simulations.