Three quarters of the earth’s surface is covered by water, an expanse so vast and deep, the power of tides and waves so immense, it is hard to imagine that we tiny creatures can have any impact on it at all. But Syd Stapleton’s latest novel gives a chilling portrayal of the damage already done to the oceans — and the ongoing destruction — by humans, the result of the greed of corporations and the governments that serve them. “The Six Mile Circle: A Sea Story” is fiction. But what Stapleton presents is very real — and well researched. He draws on his own experience at sea to paint a detailed picture of the life of a mariner. Frank Tomasini, the novel’s main character, has signed on as a deckhand and cook on ocean-going tugboats and barges making runs between the Pacific Northwest and Hawaii. These barges are loaded with freight along with some unexpected cargo. When one of the hulls is mysteriously pumped out in the middle of the ocean, a fellow deckhand gets sick and ultimately dies after contact. Frank knows he has to get to the bottom of this mystery.