Man winds up in Boston Harbor off Black Falcon Pier; rescued

No, they should not build fences around the ocean, or the rim of the Grand Canyon, for that matter.

But, on the other hand, when you live in a first world country, and you’re not out in nature but instead in a built-up environment, and you’re in some constructed place to which the public has access, such as a shopping mall, or a city street, or a public building, you naturally make certain assumptions: that flat surfaces that look like floors are safe to stand on, that walls will stand up to a person leaning on them: that there won’t be sudden unprotected drop-offs, etc.

If it’s an industrial site or a working pier I would have different expectations, but It’s effectively a park, you’d expect typical safety codes to apply. For example, barriers protecting a drop-off to the harbor

There are some places where falling in carries higher risk. If you fall in at the beach, you might get wet in the ankle-deep water. If you fall in from a wharf/quay, the water's going to be deeper and you probably can't get back out without some help.

That said, it is a pier, and if it's still being used for its intended purpose -- loading and unloading ships -- then a fence/railing is counterproductive. If that's a thing of the past, then it might make sense to install some sort of protective barrier to protect pedestrians/drivers, especially as it looks like there are going to be more offices out there.

How do you fall from a pier.
looks deep
Stay back
looks blue
Get closer.
Hmm. Is it salty?