Some cameras are equipped with a time-lapse mode. This allows still images of slowly moving objects to be taken and then combined into a movie. The camera needs to be supported on a stable tripod, and lighting needs some care.
Example animation – water lily flower opening
This is a small file – larger file here
Put the camera on a stable tripod and set the controls to take the number of images you need in a certain time period. This will depend on how slow the movement actually is. Take at the highest resolution possible on your camera.
Make sure the camera has enough power (mains is best) and that the memory card capacity is large enough for all the images too!
Download all the images to a single folder on your machine, and open your image processing software. There are plenty around to make animated GIF files, I used Paint Shop Pro. Decide on the final image size, and adjust all images to exactly that size. Be warned, if you keep the files at large size from the camera the resultant file will be huge! Run the previews in the animation software, and edit / remove frames to suit your preference. Save the file. Run it in an internet browser.