The flexible bow fingers of Surface Effect Ships (SES) and hovercraft wear away as a result of violent vibration called flagellation when the finger tips of the skirt contact with the water surface. Finger wear is one of the important problems for SES and hovercraft. A water-jet flagellator was made which can simulate the conditions of the actual fingers contacting with the water surface in order to study the durability of flexible fingers for SES bow seals. Two kinds of experiments were carried out using actual size fingers of the Mitsui hovercraft MV-PP 5. One was a flagellation test carried out over many hours from which the wear rate of test fingers was estimated. The other was an acceleration measurement test at the vicinity of the finger tips carried out over a few minutes. In these tests some parameters having influence on finger wear were changed, especially the wetted length of fingers and the water-jet velocity. The essential results are as follows. (1) It seems that this water-jet flagellator can simulate the actual finger motion contacting with the water surface because the wear patterns of test fingers resembel those of the actual hovercraft bow fingers. (2) The finger wear rate increases with wetted length, but remains almost constant above a certain wetted length. (3) The finger wear rate increases very rapidly with water-jet velocity. (4) It seems that there is some relationship between wear rates and amplitudes of finger acceleration.