I was considering getting a used fisheye lens just for fun, but realized that I probably would not find enough use for it!  Still intrigued with the sometimes very odd results, I was wondering if it could be done in Photoshop?  Low and behold, of course it can! You can make your photos look like traditional fisheye lens pictures with the black border, but I discovered that you can create a bubble effect, too!

It is surprisingly easy to do!

Open a photo with dimensions of 1×1 (fully square image).  Go to Filter>Distort>Spherize and raise the amount all the way to 100%.

If you want a border, create a new layer and grab the Elliptical Marquee tool. Set the feather value in the Options bar to 15px. Create a circle selection as large as you can without going outside the image. Press Ctrl/Cmd+Shift+I to invert the selection and then fill in black or the color of your choice!