Data collected from marine controlled-source electromagnetic (CSEM) survey has been used for hydrocarbon exploration in marine environment. The collected data is used to map the spatial distribution of seabed layers through inversion techniques. However, the accuracy of the seabed mapping depends on the quality of the survey data. There are several factors affecting the survey data; such as source-receiver geometry, source signal strength, seawater depth and geological complexities. This paper presents a method of finding optimum speed of mobile dipole source in marine CSEM survey, one of the factor affecting the survey data. The technique involved numerical solution of forward modelling using staggered-grid finite difference in spatial domain and forward time central space in temporal domain. The results show that the optimal speed obtained from the forward model can significantly improve the quality of survey data.