net 3 in such a way that the longitudinal direction of the guide elements 12 18 18 u2032 is oblique relative to the pulling direction of the device 1 the guide elements 12 18 18 u2032 at the front ends 120 thereof are fixed to the net 3 substantially at the front line 32 collection ends 121 of the guide elements 12 end freely in a collection portion 14 the collection portion 14 extends from the front line 32 onto an end portion 16 the collection ends 121 of the outer guide elements 18 18 u2032 may meet in the end portion 16 of the device 1 in an alternative embodiment the collection ends 121 of the outer guide elements 18 18 u2032 may be terminated somewhat apart from each other whereby an opening 5 is formed between the collection ends 121 as shown in fig2 in this opening the device 1 may be provided with a collection unit 52 of a type known per se for example a so called skimmer or an oil trawl the collection unit 52 may be provided with a fluid connection 54 of a type known per se which is structured to bring collected material 4 to a collection craft for example the vessel 9 material 4 located on or directly below the water surface 8 and between the doors 94 94 u2032 in the front opening 2 will encounter one of the guide elements 12 18 18 u2032 due to.