The Loch

The Loch is a science fiction novel and Legal thriller by Steve Alten, and was first published in 2005. The novel is the story of marine biologist Zachary Wallace. A sequel titled "Vostok: Sequel to the Loch" released in 2015. A third book, "The Loch: Heaven's Lake" is being released sometime in 2020.
Plot summary.
American marine biologist Zachary Wallace went on an expedition into the Sargasso Sea to witness giant squids. While there, the sonar picked up a reading that the military had named the Bloop. As the bloops closed in, the three passengers aboard the submarine witnessed the giant squid mercilessly get torn apart by a number of unidentified creatures. The submarine's acrylic bubble suffered severe damage as Zachary, Hank, and the pilot quickly race to the surface. Before reaching the research boat, their submarine's bubble pops, allowing the unforgiving Atlantic to flood in killing the pilot and drowning Wallace as he pushed Hank to safety. Miraculously, Wallace survived, and sadly, after returning to South Florida to take his position at Florida Atlantic University, he finds out that David blamed him for the destruction of the sub and the death of their pilot. Fired from the university, Zachary's life goes downhill, spending all of his savings on drinks and in nightclubs. Weeks after, he receives word that his biological father is on trial for murder. His father, Angus Wallace, lives in a village on the shores of Loch Ness in Scotland. Zachary has not seen his father since his mother divorced him and moved back to the United States seventeen years ago. However, he agrees to go visit Angus when his half brother says he is needed in the trial.
Zachary reconnects with some old friends back home and prepares to help his father. However, this is complicated by the fact that during the trial, Angus testifies that he is not guilty of the murder and that he actually witnessed the victim being attacked by the Loch Ness Monster. 
The British Tabloids go berserk and soon the Loch is full of boats and crews searching for Nessie.
Desperate to salvage his academic reputation, Zachary must discover the truth among his friends, family, the mysterious Black Knights (a branch of the Knights Templar) and other secrets.