In Nov there is an event called ARC
taking off from Las Palmas
, Gran Canaria, Canary Islands. Many boats depart for the other side at the same time. I think there is between 200 and 300 boats leaving Nov/Dec each year. Maybe 10% of this number takes extra crew.
Some people hitch a ride to the other side (the boats go to Sta Lucia first, then fewer of them continue to West Caribbean). Very few hitchhikers get a 'free' ride as this requires strong skills and is normally pre-arranged. Most pay the ride. Walking the docks, smart socialising and strong PR skills go a long way towards finding one's opportunity to cross on one of the boats.
Beware that when you arrive somewhere by boat
and want / have to sign off, then you may be required to present some form of a return ticket to the authorities. It is not a rule
everywhere but it is good to investigate beforehand. This implies having enough money
in the pocket for paying the ride there AND BACK.