No, you just need air.
Converse again.
I think I have most of the conversation in the walkthrough. I replayed that part several times.
You'll know if correct, she moves forward and if wrong she moves back in the cave.

As for the answers - take a clue word from the questions. Check the responses for an appropriate answer.
Example - she talks of time, answer with watch or clock or something related.
Remember - this is a cheeky game; so you have to be cheeky in responses too.

I noticed that and I try for the sassy response, but sometimes it just doesn't go over the way I had hoped. One time I picked the line about getting a room for 3 nights, and she reacted with what did I think she was "some kind of a floozy" and then she liked the nerve of it so I got to try again, but in the end I lost it. Now that I've rested I'll try some more, but then I will use the walkthrough when I've had enough. Hmm, I don't seem to be too hopeful of my chances do I? That will never do, Guybrush, think harder!

Go to the walkthrough.
Copy and paste the list of responses on .txt or .doc file - print it. No need to look at the spoiler below it.
Then it will be easier for you to select which is the best answers.

Guybrush did it, much to my surprise, so I didn't need to look at the walkthrough after all. Good thing since, you will never believe this, but I don't know how to copy and paste. I was about to give up trying when something happened that made me think "Wait, I feel I'm getting the hang of this, try once more." So I did, and I actually got it, boy, it was great seeing her move forward finally. Before that it was forward, then back, forward, back, and so on. The conversation got long but finally gave out. I'm thinking the something that clicked just before trying that last time was recalling the hint about "moving forward with a good answer" and that put me on the right track. The funniest answer was when she asked what would he do if she ripped his head off? Answer: Stop, thief. She said that was a new one and she liked it, so moved forward.
After the high of getting it right, I'm now stuck trying to sink DeCava's ship. So far all I can do is click on the main mast and disable their cannon and while it is down, I probably should do something, but what? Can't reach the buoy for help, can't get Morgan to help, can't go up to the wheel. Completely stumped.

Hi sierramindy,

The walkthrough says: Immediately, use the seahorse head on the cannon. Use the cannon and fire the seahorse head.

Well, duh, I used the seahorse head on The Howling Monkey, the buoy, Morgan, everything but the cannon! Thanks, Rushes.
And another big thanks to MaG. After finishing the game, I read your walkthrough. I enjoyed reading those questions and answers and now I know why the last try worked! Oh, I did like it though when the male manatee would say to Guybrush, something like "Let's go, litte buddy, that always tickled me. Had I been using the walkthrough I would not have made so many trips back and forth into the manatee and the game would have been finished a lot sooner, but it was more fun with the hints and I never did get bored (frustrated, a bit) with the game. Can't wait for #4 now! And I'll be back here again.

Great that you finished and enjoyed the game.