 Weather buoys range in diameter from 1 @.@ 5 metres ( 4 @.@ 9 ft ) to 12 metres ( 39 ft ) . Those that are placed in shallow waters are smaller in size and moored using only chains , while those in deeper waters use a combination of chains , nylon , and buoyant polypropylene . Since they do not have direct navigational significance , moored weather buoys are classed as special marks under the IALA scheme , are coloured yellow , and display a yellow flashing light at night . 
 Weather buoys range in diameter from 1 @.@ 5 metres ( 4 @.@ 9 ft ) to 12 metres ( 39 ft ) . Those <a href='null_relcl' title='1'><mark>that</mark></a>are placed in shallow waters <a href='drop_aux' title='2'><mark>are</mark></a>smaller in size and moored using only chains , while those in deeper waters use a combination of chains , nylon , and buoyant polypropylene . Since they do not have direct navigational significance , moored weather buoys are classed as special marks under the IALA scheme , are coloured yellow , and display a yellow flashing light at night . 
Weather buoys range in diameter from 1 @.@ 5 metres ( 4 @.@ 9 ft ) to 12 metres ( 39 ft ) . Those are placed in shallow waters smaller in size and moored usin only chains , while those in deeper waters use a combination of chains , nylon , and buoyant polypropylene . Since they do not have direct navigational significance , moored weather buoys are classed as special marks under the IALA scheme , r coloured yellow , and display a yellow flashing light at night .