This is nothing but bias opinion. How do we know that Bethesda didn't want to make waters more dangerous? Best way to do that is to remove water combat and add nasty fish to it. Now you have people who avoid water ways because of such thing. You find it unrealistic to not be able to fight under water, I find it unrealistic to just go trekking around in water without a care in the word. Guess all those people who died to sharks should of had a 20lb long sword with them right?
Just because you dislike a feature doesn't mean its broken. It could be working as intended and you are just upset over it. Opinion is just that, opinion, and until we have a developer that says "Whoops water is broken, we should of added under water combat." Then anything you say in such regards is pure speculation on your part.
if what you say is true, then, beth is even more incompetent. if all this water is something they wanted to make dangerous and have players either avoid or risk getting killed, then, flippin SLAUGHTERFISH certainly isn't the way to go. lol!
the waters are just teeming with danger. right.
if what you suggest is true then beth would have come up with just a tad few more frightening water creatures.
otherwise, it reeks of incompetence. therefore, i think you're wrong in your 'assessment.' though, it's merely another common rationale that people use when their skyrim is criticized.
it's a flaw or a design decision. either way makes beth look bad.
edit: and, btw, you misused the word 'bias.'