If it ' s an ocean it isn ' t technically running but with tides it ' s still definitely moving . In Bram Stoker ' s Dracula he was moved on a ship across the ocean if I ' m not mistaken , he was just placed in his coffin for the duration . Each round of immersion in running water inflicts damage on a vampire equal to onethird of its maximumhit pointsa vampire reduced to 0 hit pointsin this manner is destroyed . Speed Same as the base creature . If the base creature has a swim speed , the vampire is not unduly harmed by running water . They have a couple options here , the easiest one would be the Daywalker spell , a lvl 5 cleric spell , that you could rule would remove the water penalty as it is supposed to allow them to pass as normal . it lasts for 24 hours so if they get their hands on a couple scrolls or if you guys have a cleric . Alter self or some other polymorph effect . It does specify immersion , have the PCs encase him in a glass globe ? Vampires don ' t need to breath .