The Dredger and Construction Equipment Laboratory has developes a new sea surface cleaning system with water jets in 1976. The new system consists of water jets, a water channel and a garbage container. The rubbish collecting mechanism is that water jets induce a stream from the bow to the stern and that the induced flow leads rubbish floating around the bow into the garbage container through the water channel.
　ISHIZUCHI was built as the first boat which installs the new system in 1976. The boat has been working at Matsuyama port from that tiome.
　To investigate the capability of the new system, a field test was carried out at Matsuyama port October, 1977. This paper shows the test results and a general mechanism of rubbish collection.
　The test results verify that the new system is capable of collecting rubbish floating three meters ahead of the boat.
　The relationships between the stream velocity in the water channel, the depth of the water channel, momentum of water jets, the angle of the water jet nozzles, and rubbish collecting time are made clear.