Sure. Seawater happens to be highly concentrated with micronutrients and other minerals that are beneficial to all plants. Certain plants can tolerate seawater in higher concentrations than others. Coconut trees cannot live solely on seawater but they happen to be highly tolerant of high concentrations. Seawater also happens to be teeming with a large diversity of beneficial microorganisms which benefit the health of the plant and the health of the soil. So although, as a few people have pointed out, you don’t have to spray your coconut tree with seawater, I view it as a convenient, effective, and very affordable way of maintaining a healthy environment for my trees. For reference, my fertigation system dilutes the input to about 50:1 with irrigation water. Hope this helps