For over 100 years the Navy Records Society has published volumes of original documents that have a bearing on British naval history. Each volume is annotated and edited with a judicious hand. These invaluable tools are available by a subscription, via access to a major research library, or by one of the large free online book repositories (at least those published before the magic copyright cutoff date of 1922.) Both HathiTrust and the Internet Archive: Text have many of the early volumes freely available online under the heading of “Navy Records Society.” Update 11-18-14: Here is a linked chronological listing, with titles, of all the volumes through 1922.
Online Primary Sources from the Navy Records Society