cm floating materials caught 3 b which is are jellyfishes are cut down to for example 10 cm length by the strong thin water flow from downstream and jellyfishes so cut are easily floated in a downstream direction by the angled thin jet force in other words by the means of a high pressure jet stream in a desired direction through small holes two things are performed simultaneously the big jellyfishes are cut down to smaller pieces and they are moved by flow down to the next handling direction consequently the situation where big jellyfishes lifted on the receiving tray 5 aggregate and cannot be handled is thus avoided regarding the cutting water jet system which cuts down jellyfishes by the high pressure jet water through above mentioned small holes 10 it is possible to operate it and to apply the jet water throughout the time the main rotating removal screen 2 is rotated to send the floating materials caught 3 b to the receiving tray 5 however considering the purpose of this jet stream it is reasonable and effective to control the jet stream so that it is used only when the floating materials caught 3 b needs to be cut and is on the receiving tray 5 and only when floating materials caught 3 b exists fig4 shows a example of this control schematically and this sort of control is easily realized by installing the electromagnetic valve 40 in the cutting water supply line to the small holes 10 of the cutting water jet system and including a simple sensor 30 to detect the floating materials caught such as jellyfishes on the surface of the receiving tray 5 and by opening and closing the electromagnetic.