The X3 is waterproof but the stitching doesn't line up underwater, so you need this big bubble case for it to work normally. I picked up the dive case for my Insta360 X3 before going on a trip to the Caribbean. It's a pretty interesting accessory and I think it's worth sharing some information about.
See how X3 compares: X3 vs GoPro Max or X3 vs Insta360 One X2
It comes with a cloth case that you definitely want to keep it in, and a few paper inserts that will keep it from fogging up. There's also a mount in the box that allows you to attach it to the Insta360 selfie stick. Make sure to tighten it with the little wrench as the water is going to put a lot of pressure on that mount. You can only access the two side buttons with the case. The bottom one functions as the shutter button and the other lets you change through the video modes. It should recognize the case automatically and change into dive case mode.
The main advantage of the case is it allows you to get those amazing 360° videos underwater. You can set it up on a reef and watch the fish swim in every direction. And if you like to get follow and selfie videos underwater, you'll always get everything in the frame. I was concerned about being able to submerge with the case since it's bulky and has some air in it. It's easier than I expected, but you will need a decent duck-dive in order to get it deep in salt water.
The photos are also great. I suggest using burst photo mode for the best results. It's difficult to hold the camera still, and there is generally less light underwater, so I suggest not using HDR photos mode.
Here are some direct comparisons of the X3 and AcePro underwater and at the surface.
Buy X3 here and get a Free Selfie Stick