Most welcome, Kacper! It was a multi-step process to get the islands to float. First, the graphic must be in the SVG format. Next, visit lottiefiles.com and, using the Design tab along the top, look for the "Convert SVG to Lottie" feature listed along the right-side of the drop-down. Use the button provided to upload your SVG. You'll then be presented with a number of preset animations -- that "floating" animation is among them.
After you preview the animation and like what you see, go ahead and convert it. Once completed, access the Design tab once again, but this time select the "Convert Lottie to GIF" feature. Use the button provided to upload the Lottie/JSON file you just created. From here, you can select the size of your GIF output (200x200, 300x300, etc) and even apply a custom colored background. Convert, download, and you're all set!