There is a constant noise in the background like a small engine. Is this supposed to be? Also, in the area where the funeral barge is, the gates to an underwater cave have been opened but Indy cannot go through. He wobbles and bubbles at the opening like there is an invisable barrier. Is this a hang-up or isn't he supposed to go through there?

I don't know about the constant engine noise, but he in a previous conversation, the cons in the forum have determined that he's not supposed to go in there. There's a hole in the bottom of the floor by those 3 spikey pillar things if you feel like going through something underwater.