be an answer for the reference grid, and if close to land a traditional surveyora#39;s Total Station can do the trick. Another step is to integrate the local grid into the land- or sea-bottom-scape, for instance, in a detailed bathymetry image.
|Title||:||Manual for Activities Directed at Underwater Cultural Heritage|
|Author||:||Thijs J. Maarleveld, Ulrike Guérin, Barbara Egger|
|Publisher||:||UNESCO - 2013|