This is the only compulsory extra charge payable at the base, the deposits are refundable. This is based on the engine hours cruised, at the appropriate rate for each boat. The navigation forfait covers, fuel, gas, lock charges and other consumables. On those boats with a separate generator there is a lower hourly rate, just to cover the cost of the fuel used. Note: Most people cruise between 25 and 30 hours a week.