Let me start by saying the underwater footage of discus fish in this Blu-ray is absolutely stunning. The colors pop, the fish move gracefully, and you can see every intricate pattern on their scales. It's like having a premium aquarium in your living room.
However - and this is a BIG however - the product title is seriously misleading. Despite being called 'Aquarium 4K', this is NOT a 4K Ultra HD Blu-ray. It's standard 1080p HD. Yes, it was filmed in 4K (which explains the great detail), but then downscaled to 1080p for this release.
The packaging and description play sneaky word games about being 'filmed in 4K' without clearly stating it's presented in 1080p. As someone who specifically bought this for my 4K home theater setup, I felt pretty disappointed when I saw it wasn't true 4K.
That said, if you're just looking for a beautiful aquatic screensaver-type experience and don't care about resolution specs, the actual content is gorgeous. The discus fish footage is some of the best I've seen, with excellent lighting and composition that really shows off these magnificent creatures.
Bottom line: Great content marred by misleading marketing. If you know it's HD going in and are okay with that, you'll enjoy this. But if you're expecting true 4K as the title suggests, you'll be let down.