I finished building several new ponds last year, sited on a small seasonal creek here on my farm. One of them has a small island in it, because it worked out that it took very little extra effort.
I haven’t told my wife that I want to dig a trench to the center of the island, create an even smaller pond, containing its own tiny island.
Seriously, islands represent solitude, something that is scarce in the modern age. I totally get the appeal, and my farm is already in the middle of nowhere.