Using hydrogen fuel may help to decarbonize maritime transportation. This paper presents an estimate for the mass of hydrogen that would be needed to power the current fleet of crew transport vessels used for maintaining the German offshore wind farms. The estimate is based on a calculation of the marine diesel oil consumption of the current fleet. We use vessel position data, weather data, and diesel consumption estimates to perform this calculation. Various hull shapes are used in small coastal vessels. This creates a challenge to estimate their energy needs. As a shortcoming, certain effects are excluded from the current estimate. However, this work presents an approach that can be improved and used for estimating hydrogen consumption in future scenarios. In these scenarios, a vessel type and parameters can be set. While here the challenge was to create a generic model that can be applied to multiple types of vessels.