1: When the ferry left Belgium, Percy had a meal.
2: Then he watched two videos.
3: While he was having a good time, the people inside the trailer were getting hotter and hotter.
4: First they took off their clothes.
5: Then they drank all the water they had.
6: Soon they found it difficult to breathe.
7: They realized that if they didn't get fresh air quickly, they were going to die.
1: ‘leave’ meaning ‘depart’; punctuation (comma between clauses)
2: separate sentence (‘then’ is a conjunct (a ‘sentence connector’))
3: past continuous in ‘while’ clause and in main clause; ‘get (=become) hot’ comparative adjective + ‘and’ + comparative adjective
4: ‘take off’ (phrasal verb)
5: ‘all the water they had’ (adjective clause, ‘that’ omitted)
6: ‘found it difficult to breathe’ (postponed subject)
7: meaning of ‘realize’ (come to know); past tense real conditional