Complex sentence: There is no regularly scheduled ferry service to Blakely Island, access is only by boat, arriving at the marina at the northern tip of the island, or by light plane, arriving at Blakely Island's airstrip.
Split into simpler sentences: There is no regularly scheduled ferry service to Blakely Island. Access is only by boat, arriving at the marina at the northern tip of the island, or by light plane, arriving at the island's airstrip.