Complex sentence: Its main use is to ferry passengers to the West Arm of Lake Manapouri where they can continue on to Doubtful Sound, it also provides easy access to Lake Manapouri for recreational boat users.
Split into simpler sentences: Its main use is to ferry passengers to the West Arm of Lake Manapouri, where they can continue on to Doubtful Sound. It also provides easy access to Lake Manapouri for recreational boat users.