The RTA has announced the timings for the Dubai Ferry during the holy month of Ramadan 2015 and there are some changes to the schedule so you should check this out before embarking for a trip:
Most notably there is now only one ‘tourist trip’ running from Dubai Marina and the other trips are from Marina to Al Ghubaiba and vice versa.
Al Ghubaiba to Dubai Marina – 11am and 6.30pm
Dubai Marina to Al Ghubaiba – 11am and 6.30pm
Tourist Trip from Dubai Marina – 5pm
These trips run every day.