Water buoys analog to milestones

[Kadaban]

Hey there.
Just had an idea recenty when following the same old water way for the <insert_large_number_here>th time.

Would it be feasible to add a kind of buoy system like the milestone system on land but for water? This would certainly come with it's benefits as people could much more easily follow well used trails. But on the other hand it's also dangerous as people would know your route if you were to blindy (maybe even afk) follow it. (Pirates anyone?)
I know construction or "destruction" on water would be a bit of a challenge as to not allow blocking the waterway by spamming buoys. Maybe make them passable by default?

Anyways I'd like to hear some critic on this.