It's hard to believe that, after serving in the U.S. Navy for years and around battleships, that Gilligan wouldn't know what nitroglycerin was. Navy personnel are always trained in ordinance and it's primary construction ie., chemicals and compounds used in their manufacture.
Had Gilligan really swallowed nitroglycerin, he would've died from system shock and internal hemorraging almost instantaneously, let alone exploding.
In the beginging Gilligan gets his water from the lagoon, but the lagoon is salt water, its connected to the ocean.
Gilligan: I can't move.
Lovey: Oh you poor boy. Where does it hurt?
Gilligan: I don't feel a thing.
Lovey: You don't feel a thing?
Gilligan: Mrs. Howell, I might blow up!
Lovey: Oh don't you dare get angry with me.
Gilligan: I mean blow up for real. I drank some-
Lovey: Oh that's why you don't feel a thing. You've been dipping into Mr. Howell's private stock. Demon rum is your worse enemy.
Gilligan: No, I didn't drink rum, I drank nitroglycerine.
Lovey: Oh mixed drinks are even worse.
Gilligan: Hey Professor, great news. They stopped.
Professor: Who has stopped, Gilligan?
Skipper: The spouts stopped spouting.
Gilligan: The volcano stopped volcanoing.
Gilligan: That too.
Professor: Unfortunately, it simply means that the gases Professor:are gathering force and could explode at any moment.
Skipper: That's terrible!
Professor: However, there is a way to neutralize the volcano by countering its energy force with an equal energy force.
Gilligan: Oh that's terrible!
Professor: No, that's good.
Gilligan: Sounds terrible.
Professor: In layman's terms, if I could explode a bomb in a tunnel near the base of the volcano its force would blow it out the same way you'd blow out this candle.
Skipper: But Professor, where are you gonna get a bomb that big?
Professor: From materials right here on the island. As a matter fact, I'm making a crude form of nitroglycerin powerful enough to blow off that entire mountaintop.
Gilligan: You're making nitroglycerine?
Professor: Well yes. Sulfuric acid from the crystallized copper in the caves, glycerol from papaya seeds, and potassium nitrate from the rocks at the lagoon.
Gilligan: You hear that? He's making nitroglycerine.
Professor: Any questions?
Gilligan: Yeah. I have a question.
Professor: Good, Gilligan. What's your question?
Gilligan: What's nitroglycerine?
Gilligan: Sometimes I wish the earth would just open up and swallow us up. (There is an earthquake) Skipper, that never happened before.
Skipper: I hope it never happens again.
Gilligan: I know something else that's never happened before. It never snowed.
Skipper: Gilligan, it doesn't snow on a tropical island.
Gilligan: Yeah, look. (flakes fall from the sky.)
Skipper: I wonder if we're on the Christmas Island.
Gilligan: I'm trying to make some snow balls, but it won't pack.
Professor: It isn't snow, Gilligan. It's volcanic ash.
Ginger: Gilligan, the hugging and the kissing is just to show how much we love you. There's no one in the world that I love as much as I love you.
Gilligan: Is that the truth?
Ginger: If I'm not telling the truth, may lightning strike. (There's a bright flash and a roar.)
Mary Ann: Dishwashing with running hot water. You know what that means?
Ginger: No more broken nails.
Mary Ann: No more chapped hands.
Ginger: As Davy Crockett said when he shot the last Indian: "No more red skin."
Lovey: Thurston, after all, Gilligan found the hot water. Therefore he owns it.
Thurston: My dear, I know he found it. I know he owns it. But I intend to merge his hot water company with my cattle company.
Lovey: What will that give you?
Thurston: Boiled beef. Lovey, my dear, I did make a funny.
Gilligan: Maybe you could help me solve a problem. How do I get the hot water to camp without carrying it?
Professor: Well that's very simple. Just use some bamboo rods to make a pipeline.
Gilligan: Oh thanks, Professor. Talking to you is like looking up the answers in the back of the book.
Skipper: Gilligan, can't you hear everyone yelling for hot water?
Gilligan: I can hear them if I was in Hawaii.
Skipper: Very funny. Besides, what were you doing up in the jungle?
Gilligan: I got tired of going to the lagoon for water and bringing it back to camp and boiling it to make hot water.
Skipper: Well where else are you going to get hot water? Out of a hole in the ground?
Gilligan: How'd you know?
Skipper: Well I just figured that you…How do I know what?
Gilligan: That I get hot water out of a hole in the ground.
Theme of episode: Near misses don't count; the result does.