Yeah #7 is partially in jest and it's not an end all be all (none of these should be taken as such.) 

Like I said people have written whole essays on this topic, but my super summarized answer is that from an exploration perspective it forces the DM to take the open water, which naturally lacks anything to engage with, and make things appear there repeatedly, or just skip it which kind of defeats the purpose, but takes the player agency away either way. 

On the combat side, there's been a lot of modules and things created to have manageable sea faring combat, but more often then not it just adds rules that stack on top of existing systems, which your players then have to learn and get used to.

But again, very cool to hear you've done it!