Airborne laser bathymetry is an efficient and area-wide measurement method for the detection of the permanently changing water bottoms of inland waters and shallow water areas close to the coast. In this method, a short green laser pulse is emitted, which interacts with all objects along the laser pulse path (e.g. water surface and bottom). The backscattered laser pulse components (echoes) are digitized and stored in a high temporal resolution measurement signal (full-waveform). However, the measurement method is limited in its penetration depth into the water body due to water turbidity. The water bottom echoes become weaker as the water depth increases until they are no longer reliably detectable. This work shows how novel methods can be used to detect weak water bottom echoes in full-waveforms that are no longer accounted for by standard processing methods. In the core of the work, two methods are presented which are based on a joint evaluation of closely adjacent measurement data. Under the assumption of a steady water bottom with low to moderate slope, the combination of several full-waveforms leads to an improvement of the signal-to-noise ratio and an enhancement of weak water bottom echoes, which consequently can be detected more reliably. The results show a significant increase in the analyzable water depth (up to +30 %), allowing a much larger area of the water bottom to be covered (increase up to +113 %). Comprehensive analyses of the results proved that the added water bottom points are a good representation of the water bottom. Thus, the methods developed in this work constitute a valuable contribution to increase the efficiency of airborne laser bathymetry described at the beginning.