Fuel hoses require the correct ISO standard (7840) to ensure that they are of sufficient quality and durability to perform to the standard required on a craft for use on the inland waterways.
An inboard / fixed fuel tank will have a vent to prevent the engine creating a vacuum when the fuel is used.

It is recommended that the position of the tank vent / outlet is atleast 100mm higher than the filling point (to prevent spill upon over filling).
The vent must be positioned away from potential sources of ignition.
Each vent must be fitted with an effective flame arrester (tank vent with gauze to prevent flash ignition).