I also have a problem with no mobs. Sure I can spawn them with a egg but they won't spawn naturally, except for the villagers, which brings me to a unreported problem I have... THEY WON'T TRADE! I "right-click" (in quotes because i'm on a Macbook and it's hard to right-click so I changed the button) on the villager and it says in the console, "you still need 60 more minutes of dive time! No trimix gas for you!". Please help.

There is no villager trading in 1.10.2 currently. The villagers will give you a trimix gas for your scuba gear if you right click them with your dive computer and you have been underwater with your scuba gear on for 60 minutes IRL time.