What's in a Title?
Well, quite a lot actually. The Vanishing Tide had at least six titles before it became The Vanishing Tide. 'Blame' (too YA), 'Saltwater' (somebody else beat me to it the year before), 'Between the Water and the Sky' (too long, too literary and not easy to remember. There were others.
For my genre, which is reading group, It helps if a title reflects the plot or setting, or even a thought in the text. I personally find it hugely irritating if I buy into a title that doesn't reflect the book I'm reading.
When a title is proposed, the name needs to be Googled and looked at in Amazon to make sure other titles don't already exist with that name. However, if a book has been published many years ago with the same name, it is less of an issue unless you want to use something that is very famous. Nobody is going to propose '1984' or 'Animal Farm' as a title, because these titles are indelibly linked to George Orwell.
My second novel, SWIMMING HOME, has the same title as an excellent read by Deborah Levy, but as this book was published in 2011, has a different genre and different setting, it is seen to be separate enough.
Finding a good, punchy, memorable title based around water that hasn't been used is more difficult than you think!