UnderWater Acoustic (UWA) channels are narrow bandwidth and typically affected by some interference due to propagation, Doppler effect, noise and possible disturbing signals originated by different acoustic sources. Orthogonal Frequency Division Modulation (OFDM) is an effective answer to such impairments. Resource management in the framework of OFDM usually makes use of channel knowledge without taking care of its cost. This work tackles with the dualism between channel estimation and channel prediction and its impact on adaptive modulation, both from a bandwidth and power point of view also in the presence of acoustic interference. The main result is that adaptivity is worth even if requires some processing both at the transmit and receive sides. © 2013 IEEE.