Possible approaches to a boat ramp on Kootenay Lake witnessed in British Columbia, Canada

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I have been vacationing on the Kootenay Lake for many years at a camp ground called Woodbury Resort. The resort is located 2 miles north of Ainsworth Hotsprings. For the past 5 or 6 years when camping there I have slept on our boat which is located in slip number 1 in the marina. It is directly beside the boathouse and gas dock and no more that 15 feet from the metal ramp leading from shore to the marina. Because of the location, I can see and hear everyone that comes and goes from the dock and after many hours spent sitting on the boat in that location, I know the sound of people approaching on the dock and from shore and that is why I am writing this to you. When sleeping on the boat I have a tendancy to wake at every stupid noise of someone around on the dock, but what started to get my attention was someone or some thing entering the marina late at night usually after 12 but before 3. What was unusual about this was first the time spent on the ramp to the marina...