The game has a bit of an awkward start, and the graphics on the title screen are a little off-putting. However, once I got into the gameplay I was pleasantly surprised! You control King Neptune on his quest to get the magic pearls back from some evil entity. Simple enough.
It’s easiest to compare this game to Legend of Zelda in how it seems to be structured. You can move up down left and right (except here you are swimming in a side view, rather than overhead perspective). You can seemly go anywhere and begin your quest to find all the collectables you need to progress. Pushing select shows a map of where you are, and your current collection of items, how helpful.
Nothing stood out as remarkably bad. The controls are responsive, although they have that characteristic underwater slipperiness, at least it makes sense here. The music and sound effects are there, and the background for each different environment is distinctive. Although, literally compared to Zelda it isn’t as good, I would have been happy to own this as a kid.