Simplify the following text for a Grade 5 native English-speaking person.
Original: During the next 10 days much difficult country was traversed but they then came to more level and open land , and on 16 December they sighted Port Phillip in the distance .
Simplified: During the next ten days it was hard traveling through rough country , but they did get to more level and open land . On December 16 , they saw Port Phillip Bay .