Data rate and reliability are two critical figures of merit in communication systems, especially in underwater acoustic channels with limited bandwidth and double selectivity. In this paper, we will present our recent results of four rate-or reliability-oriented underwater acoustic communication schemes. We will show that the rate-oriented basis expansion model (BEM)-based single-carrier scheme provides high transmitted data rate with satisfactory performance at the price of high receiver processing complexity and large receiver array. In practice, however, not all receivers have large number of hydrophones and can afford such complexity. Examples include small-size sensors or autonomous underwater vehicles. Hence, we also develop and test reliability-oriented systems, where resilience against the channel variation is facilitated by carefully designed transmitter processing while keeping the receivers simple. We will show the advantages of our schemes by comparing with the existing alternatives. All four schemes are tested in recent sea trials.