Paddles and plastic sheaves

Observed on the block that supports the beam trawl aboard a visiting Belgian beamer, the use of plastic for the sheaves....
as a rule, all the Belgian boats hang up their cod-ends while in port.....
these are dual-purpose boats that can go mid-water trawling during the winter months....
recognise that face cutting through his footrope?
in the relatively sheltered confines of the harbour, someone gets instructions on sea-kayaking