Why is there 0% VAT on my invoice?

This depends on the specific location where the delivery took place. The VAT rates are configured directly by the locations themselves (such as seaports); as a company, we have no influence over this setting.

For certain deliveries in ports, such as supplies for seagoing vessels, it is legally permitted to apply a 0% VAT rate. Because your delivery took place at a location that falls under this regulation, the zero rate has been correctly applied to your invoice. 

For more detailed information regarding the conditions of the 0% VAT rate in shipping (available in Dutch), please consult the website of the Dutch Tax and Customs Administration (Belastingdienst): Delivery of ships and aircraft - Belastingdienst