Maukaveli

I've finished both the Kanto and the Hoenn region, beat both elite four, finished all of the seven islands and have literally done everything I can as far as progression in the game. I trained a few pokemon to lv 100 but that got boring, I tried hunting for shinies but I honestly just don't find it fun, etc. What else is there to do to keep the game entertaining? I really enjoy it, but it seems as if there's nothing left to do.

Wow, thanks... I can't believe I missed that. Sorry for that, but I really appreciate the help.

To continue on with the game in the Hoenn region I need to dive beneath the Seafloor Cavern and check out the submarine and go through all the maze and then surface so I can move on with the game. However; whenever I dive down to enter the Seafloor Cavern I just dive back up in Sootopolis City and I can't do any of the parts required to move forward it just straight up pulls me above to Sootopolis City and I can't move on with the game. I've done everything required, defeated team magma and aqua when I needed, got all previous seven gym badges, acquired Dive from Steven, etc. What's the problem or is my game just glitched?