The data is provided by the National Oceanic and Atmospheric Administration (NOAA) National Data Buoy Center (NDBC), a part of the National Weather Service (NWS). NDBC designs, develops, operates, and maintains a network of data collecting buoys and coastal stations.
The buoy I'm interested in does not have swell data or is missing something else
NDBC provides hourly observations from a network of about 90 buoys and 60 Coastal Marine Automated Network (C-MAN) stations. All NDBC managed stations measure wind speed, direction, and gust; barometric pressure; and air temperature. In addition, all buoy stations, and some C-MAN stations, measure sea surface temperature and wave height and period. Conductivity and water current are measured at selected stations. NDBC managed stations typically have a 5 digit name like 42035, 41009, or 41012.
Most NDBC stations are located at sites determined by NWS forecast and warning requirements. Some are installed and maintained in areas identified through reimbursable funding agreements with other agencies and private sector institutions. Even though buoys are not installed in as many locations as we would like the locations of buoys have been purposefully picked to allow all locations to infer local conditions based on nearby buoys. If there is not a buoy in your immediate location please find a nearby buoy and base your local conditions off of that buoy.
NDBC uses commercially available sensors such as anemometers to measure wind speed and direction and barometers to measure atmospheric pressure. On the buoys, wave data are collected using an accelerometer which measures the vertical acceleration every 2/3 of a second for 20 minutes. Wave heights and periods are mathematically calculated from these time-series accelerations.