The "World Is Not Enough" N64 Question?

What the heck do you do to get out of the upside down Sub? I just swim through that hole underwater and then get stuck in there. What do you do next? Please Help.

Btw I did my research on walkthroughs and there isn’t one yet for this game. To new.

Thanks in advance if you can help me.

There’s a wlakthrough here but you have to register first.