Skills on the vessels (6)
I believe the answer is:
crafts
This clue is a double definition.
'skills' is the first definition.
(I know this)
'the vessels' is the second definition.
('craft' can be a synonym of 'vessel')
'on' acts as a link.
(Other definitions for crafts that I've seen before include "Hand-made objects" , "Skilled trades" , "Boats; skills" , "Builds" , "Occupations requiring special skills" .)