Using the Panchromatic band for water column correction to derive water depth and spectral bottom signature: Landsat 8 OLIP bandset used for this work Purple=1, Blue=2, Green=3, PAN=4, Red=5, NIR=6 and SWIR1=7 
Collaboration with Fabio Favoretto, Ph.D Student, Coralline Algae Ecology Grupo Interdisciplinario de Ciencia Ambiental, Universidad Autonoma de Baja California Sur Carretera al sur km 5.5  La Paz favorettofabio@gmail.com 
Using pan sharpened images in this study Pan sharpening using Rstudio with Brovey method 
N=187,044 

decimeters 

Red outliers 
nbMin=0 ==> N=187,044 nbMin=2 ==> N=147,620 nbMin=10==> N= 85,840 
download ASCII textfile  format: XUTM YUTM ZDTM Z4SM ... ASCII textfile 3MB from GoogleDrive at https://drive.google.com/open?id=0B6EgWTY7EkNxamQ4bFZVT005LU0 
Seatruth ZRecordedZComputed in cm ZDTMCombinedDepth
Tide height
 
Combined Depth and profile_black  DTM and profile_black Please note isobaths abutting to the shoreline! Fabio: please send me a shapefile of all depth points you used to produce this DTM, so that I can map them here 
Regression CZ vs ZDTM for all points which have both CZ and ZDTM: N=187,044  Histograms CZ and ZDTM for all points which have both CZ and ZDTM: N=187,044 
Regression CZ vs ZDTM for all points which have both CZ and ZDTM for all bins with at least nbMin=10 points: N=85,840  CZ and DTM along profile_black 
operational diffuse 2K This fuzzy regression does not prove much in this complex and variable hydrologic environment: we would need a LIDAR or MBES DTM Still, in the 1020 m depth range, it demonstrates two sensitive things==>  operational diffuse 2K retrieved depths in meters only need a tide correction
the PAN solution is a good operational option 
About the Soil Line assumption Spectral water column corrected bottom reflectance is the main unknown for all SDB methods Therefore, all methods resort to some assumption in this regard
In the end, all methods yield a more/less biased depth result: there is no escaping that  About the Soil Line assumption In this study case: (please help me ensure I have it right!)
Therefore also, computing a seatruth linear regression with a slope=1 becomes tricky, to say the least 
By default in 4SM>>==>>
 >>==>>What we see here

GSD 15m; Coregistration; DTM
 Time series

small ROI
 extended ROI

Clearest waters
 Clearest waters

Fabio, if I may Your DTM is going to be a weak link in this story. Just think of bathymetric lines abutting the shoreline.  Fabio, if I may So, maybe Andy would not mind contributing a more realistic DTM from your very "fish finder" measured depths. Sorry, I can't offer to do it myself. When I say realistic, I mean: limited to areas which are adequately/densely informed. I suppose you would just provide us with list of XUTM YUTM YourMeasuredDepth as an ASCII textfile, mentioning Depth Datum (tide correction), UTM Datum and Zone. And I could also use a shapefile of this data, as. mentioned above 