Silent Thunder: Hannah Bryson series #1 by Iris Johansen

The first book in the Hannah Bryson series by Iris Johansen and Roy Johansen. The story introduces Hannah Bryson, a marine architect, who gets involved in a dangerous adventure when she's tasked with inspecting a newly-acquired Russian submarine, the Silent Thunder, for exhibition in a maritime museum.
During her inspection, Hannah discovers a hidden message within the submarine, leading her to uncover a deadly conspiracy. With the help of her brother, Connor Bryson, and a former Navy SEAL, Nicholas Kirov, Hannah must navigate a web of deception and danger to unravel the truth.
It's a thrilling ride filled with suspense, action, and unexpected twists.