>>32578342thing is though, large animals are vastly easier to discover than small ones
even if we couldn't see the animals themselves, something larger than a blue whale would leave a massive and very obvious mark on it's ecosystem
and when it comes to the deep oceans, guaranteed we don't know even half of what's down there, but it won't be particularly large simply because of how much energy a large animal requires and how little there's of it down there.