How seriously do you take your work? The level of your perfectionism will affect your choice of the head. The Manfrotto MH055M8-Q5 is relatively inexpensive, so the price alone might justify trials. And the eventual corrosion will not feel so bad.
If you plan to do proper fluid pans/tilts with a tripod, you'll need to weigh it down for it to become a stable platform. You'll need more weight than without video pans/tilts. For a proper job you might consider selecting such a tripod that its legs can be spread out more than the normal 30-60 degrees. A larger/heavier tripod with add-on weights will affect your dives as well. Consider using lift sacks.
However, you might want to consider other choices as well:
A monopod would be lighter and easier to transport whilst swimming. You can perform tilts and pans even without a video head.
A dedicated small u/w tripod like the TLC tripod. Corrosion will be far less a problem.