Complex sentence: After they failed to leave, due to unavailability of transportation, the government extended their time to 48 hours; within the 48 hour time, a lone ship was leaving for Jamaica, which they boarded.
Split into simpler sentences: After they failed to leave, due to no forms of available transportation, the government extended their time to 48 hours. Within the 48 hour time a lone ship was leaving for Jamaica which they boarded.