So after they throw one cigarette away, the boat is lighter by the weight of one cigarette. So, it's a cigarette lighter, ie, play on words, it's that thing you light a cigarette with.
At first I didn't get it.... Then I reread it... Then I read it again... Then I still didn't get it... Then I read it a third time and about half way through I was like "oh... Oh damn!"
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