Rather hard to tell but I'm assuming a clove hitch as it is commonly used by boaters.

From the 1897 monograph "Fisheries of the Indian River":

The Indian River is a brackish lagooon 120 miles long between the Florida mainland and the outer barrier islands. This picture probably was taken near Jupiter Island. It would be quite difficult to show the actual location today but this view from a bridge in Hobe Sound shows what it might look like.

By the way, Frederick Delius was on an orange plantation along the St. Johns River, much farther north than this location.

I grew up in Eau Gallie (merged with Melbourne in about 1970), on the Indian River. There it's much wider, nearly two miles. Wish I could have seen it then.

It's interesting to see the 1888 date carved in the palm tree along with some initials above it. Seems to be C C P maybe?

Anyone know what kind of knot that is?

The German/English composer Frederick Delius lived along the Indian River for two years at just about this time, managing an orange grove.

Delius had little interest in citrus fruit, but he absorbed much in the way of local lore and musical ideas, especially spirituals, and these are reflected in his later compositions such as "Florida Suite" and "Appalachia."