Passive time reversal uses a set of matched filters corresponding to individual channel impulse response to reduce intersymbol interferences (ISIs) in underwater acoustic communications. Because of residual ISIs after time reversal, a coupled single decision feedback equalizer (DFE) is necessary. The coupled DFE uses a fixed tap number applicable to most shallow oceans with less user supervision. However, this correlation-based DFE needs the training sequence to estimate the individual channel response and initialize DFE, which decreases the effective bit rate and increases user supervision. We therefore in this paper propose a new blind structure of time reversal coupling with DFE, and it can complete multichannel identification and equalization at the same time without the training sequence. This new receiver has a reversible structure. In the first mode, it is linear and adapted by blind algorithms, e.g. constant modulus algorithm (CMA), to estimate the multichannel impulse responses and initialize the equalizer. In the second mode, the receiver becomes correlation-based DFE. From the viewpoint of user supervision and spectral efficiency, the new structure with no training sequence is more attractive. The blind correlation-based DFE exhibits the same steady-state mean square error (MSE) with the trained structure, and has been validated on real underwater communication data.