Our coasts are open to attack from the oceans. There are many options open to the engineer attempting to limit the damage to our coastline. This work tested the Seabee, a particular variety of concrete armour unit, for use on sea walls, breakwaters and revetments. The research was performed in a regular wave channel with a level bed 13m long, side walls of 465 mm (extended to 650 mm in the region of the model) and a width of 455 mm. A constant water depth of 300 mm was maintained throughout. The research explored the influence of the fundamental design parameters of the Seabee unit on run-up and reflection performance. By careful selection of wave climate it was possible to generate regular, well formed waves which covered both the desired range of wave steepness and Surf Similarity for slopes of 1:1.5, 1:2.1, 1:2.4, 1:2.6 and 1:3.6. Measurement of reflection and run-up was by means of capacitance probes attached to a PC based data logging system. Data analysis programs were written which run under Matlab®. Smooth, non-porous slopes were tested at each gradient as well as monotonic Seabee arrays at an assumed model scale of 1:20. The unit heights tested were 0.52 m , 0.68 m, 0.88 m and 0.96 m with an axial bore of 0.65 m. A layout was devised utilising units of different heights in an ordered pattern, called an upstand array. Tests of smooth slope run-up demonstrated good agreement with the generally accepted empirical models, including prediction of wave breaking. Two mathematical models were derived which fitted the observed run-up and run-down on the Seabee arrays with very good correlation. Statistical analysis showed that the run-up performance of the Seabee unit is largely dependent upon the unit aspect ratio - the taller units exhibiting greater run-up. The same models were fitted to the upstand layout which showed considerably reduced run-up. The performance of the Seabee was shown to compare well that that of other armour types. In addition, a constant relative roughness factor was shown to be unsuitable for predicting run-up on Seabees.