The feature-set and price point of the DJI Osmo Action make it pretty obvious from the get-go that it's an attempt to undercut the GoPro HERO7. Does it succeed? Like all things, it's complicated. The front-facing screen is a boon, the stabilisation is just as silky smooth as the HERO's, and it's wallet-friendly price is nothing to sniff at. That's not to say it's perfect; there are a few lag issues at high resolutions, the app can be unreliable, and video from the HERO is a touch flatter, which counts in professional realm when it comes to the grade. For an affordable alternative to the HERO7 Black though, the Osmo Action is a fantastic choice.
The highlight of the RX100 VI over the RX100 VA is its unprecedented macro capability. The zoom on the 24-200 mm f/2.8-4.5 zoom lens cannot be beaten by other compact underwater setups. Details captured with this lens are remarkable. When combined with a wet macro lens (diopter), the realm of super macro photography is attainable. The tiniest details of the smallest subjects can be captured with this set up (once you get a little practice in of course).
The A7 III, with its compact and ergonomic design, has been a very popular camera for video recording. The battery life is drastically improved compared to the previous A7 Series cameras, which was a primary complaint of Sony Alpha users and is particularly beneficial for underwater video, as it allows you to shoot for much longer without the need to open the housing. The A7 III also has dual SD card slots, which play an additional role in the maximum allotted time you can record underwater without having to open the housing. The auto-focus during video works very well.
Action cameras like GoPros have their advantages too though. They're generally much smaller than waterproof compacts, making them lighter and easier to mount via a chest harness or helmet mount or similar. The best action cameras also tend to have better video specs, offering pristine 4K in high frame rates, which many waterproof compacts currently lack.
What is a good cheap action camera?
The rest of the camera's highlights include Wi-Fi for smartphone connectivity (via an app), GPS, a built-in eCompass, and a temperature sensor. You can embed data from the sensors in your images when you edit them, thanks to a dedicated app by Olympus. And the 3-inch LCD display means navigating through all the camera's features is easy. The screen is considerably sharper than one found in the device's predecessor.