In this experimental work, sloshing tests were performed with containers filled 1 with water at 50% of their volume capacity. Two boundary conditions were considered: un- 2 coated containers and containers with hydrophobic coated walls such as in [1]. In addition, 3 several aspect ratios λ (container width over length) were considered. We characterized two 4 regimes: the first one when the container is periodically forced at a frequency lower than its 5 resonant frequency and the second one after the forcing is suddenly stopped. In each case, 6 the amplitude of the waves was measured. Several surprising results were found. First, in 7 the forced regime, the sloshing amplitude was lower in the hydrophobic containers than in 8 the nonhydrophobic walls, despite the free-slip condition in the former case. Second, the 9 free damping after sudden stoppage was much higher with the hydrophobic walls than 10 with the uncoated containers. This behavior is explained by the collision of waves with 11 oil-coated walls, which decreases the load pressure. Finally, it was found that the damping 12 depends on the dimension of the container through λ and is greater when λ = 1.0. These 13 experimental findings open the way for further innovative research.