Dune foot revetments
A dune foot revetment is similar to a seawall. Its purpose is to prevent dune erosion due to cross-shore transport during storm surges. The revetment is specifically located at the dune foot. Again, an important design criterion is the expected erosion depth at the toe of the revetment. A rather spectacular form of dune foot revetment has been built on Sylt, Germany (see Fig. 87). Tetrapods prevent a direct attack on the dunes.

Dykes
An extreme version of a seawall is a massive dyke. A dyke is used at locations where no backshore is present (see Fig. 88 and Fig. 89). Due to the absence of backshore and dunes, the dyke looks massive. Design criteria are similar to the design criteria for a seawall and a dune foot revetment.