[Tagging] dock=tidal

[Malcolm Herring]

On 29/05/2015 13:16, John Eldredge wrote:
> That is just one of the common meanings of dock. Another common meaning
> is as a synonym for pier, an above-water structure used to give access
> to a ship.

You are referring to the en-us usage of the word "dock", which covers 
piers, pontoons & the like. OSM renders waterway=dock as water, as would 
be expected for en-gb (and IHO) usage.