I wouldn't say universally bad. I live in Seattle, and there are some restaurants on the water that I like.

The way I think about it is this: the restaurant has to pay for the real estate, and that cost must get factored in somehow. Water views aren't cheap. So you can get good food on the water, but you'll be paying for the view.

Shipping of sea food is expensive so even the cheapest distant resteraunt will pay for premium prices since the difference isn't that much. Near the shore you can save buying cheap - but if you know what you are looking for you can buy the best off the boat for cheap.

Less true if you're talking about seafood "shacks." Tons of good places serving lobster rolls and steamers on the ocean in Maine for example. But, yes, for fancier restaurants especially in cities, the best views often don't come with the best food.

El Bulli was considered the best restaurant in the world until it voluntarily closed and it is right on the Mediterranean with a dock. The web site even had directions to reach it by boat.

If this is true at all, it only applies to cities. Many fantastic seafood restaurants are on or near the docks in regions economically dependent on seafood production.

If this were true, the best seafood in Australia would be in Alice Springs.

Conversely, I have one piece of life advice for you: Don't eat seafood in Alice Springs.