I'm a pleasure boater

You have a boat and you want to sail on the Garonne, stop at Cadillac while waiting for the opening of the lock in Castets-en-Dorthe?
Stop at Cadillac to visit its historic center and replenish yourself in the city’s shops within walking distance from the port.
Before docking, contact the tourist office to check availability and carry out administrative procedures.
Prepare your insurance certificates, certificate of homologation and registration that will be required before your stopover.
The tourist office will then give you the authorization to moor and will issue you the access code to the pontoon.
Consult the rules of use here
Monthly pricing, long term, unlimited touch but also low season (from 01/10 to 31/03) has been implemented.
The prices of dock are downloadable here
Also, the inhabitants of the Community of Communes Convergence Garonne benefit from a 10% discount on all rates (on presentation of a proof of residence of less than 3 months). An agreement will then be established.
Watch out for the Mascaret: during high tide coefficients, it is felt at Cadillac. Moor your boat from the bow downstream and double the moorings. 
To calculate the hours of passage of the tidal bore, add 2 hours to the BM from Bordeaux. More info here