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Garmin Virb 360 available here: https://goo.gl/wz4ooF (Amazon) or https://goo.gl/hgOaeX (B&H Photo)
I tested my Virb 360 in a swimming pool. I was surprised that despite the expected refraction, the stitching looked much better than on other 360 cameras I have used underwater (without a spherical housing) such as the Keymission 360.  However, when the camera is tilted, the stitching looks weird.  But as long as the camera is vertical, the stitching looks excellent for a 360 camera used underwater without a spherical housing.  Full resolution photos here: https://roundme.com/tour/166292/view/424195/