Private wells in coastal areas can draw seawater, causing them to have a high salinity. It is difficult to determine how much seawater is safe for landscape plants since every plant has a different salt tolerance.
However, here are some things to consider: Sea water has an average salinity of about 35,000 parts per million. According to horticulturalists at URI Cooperative Extension Education Center, water with a concentration over 500 parts per million begins to be unhealthy for even the hardiest of plants. However, each plant type will react differently to the amount of salt in water, depending upon its sensitivity.
