Elevation observations and tidal predictions for this station are reported to NGVD 1929. To convert data to NAVD 1988 subtract 0.95 ft. To convert data to MHHW datum subtract 2.20 ft. To convert data to MLLW datum add 1.13 ft. These corrections vary from site to site. 
NGVD
1929 is the National Geodetic Vertical Datum of 1929,
formerly called "mean sea level" or "Sea
Level Datum of 1929." NGVD 1929 was a general
adjustment of the firstorder level nets fit to mean sea
level at 26 tide gages in the US and Canada.
NAVD 1988 is the North American Vertical Datum of 1988, which is a geodetic datum derived from a general adjustment of the firstorder level nets fit to 1 tide gage in eastern Canada. MHHW is mean higher high water, which is a sitespecific datum determined by averaging the highest of the 2 high tides that occur each day over a 19year tidal epoch. For tide gages with less than 19 years of record, this datum is estimated by correlation with longterm tide gages. MLLW is mean lower low water, which is a sitespecific datum determined by averaging the lowest of the 2 low tides that occur each day over a 19year tidal epoch. For tide gages with less than 19 years of record, this datum is estimated by correlation with longterm tide gages. 
Additional sensor graph(s) available (click on graph or sensor name)
Water elevation, astronomicaltide elevation, and residual water level Graph updated every 15 minutes
Phycoerythrin relative fluorescence (fPE), water, in situ, relative fluorescence units (RFU) 

