Like all the tools in Photoshop there are more ways to do the job. But the Patch tool is quick and pretty accurate.
We start with this picture and duplicate the background layer (Cmd or Ctrl J).
We want to remove the boats in the background to get a cleaner image.
Select the Patch Tool (J)
Now make a selection around (a part of) the boat and move your pen/mouse the the left or right.
Repeat this several times to remove all the parts. You can always combine more techniques to get a good result.