The Operative by Theresa Beachman

Hunted for her discovery, only one man can protect her.

Marine biologist Alina Andersen has loved sharks since she was a little girl. So, when she suspects decaying nuclear submarines are polluting their Arctic breeding grounds, she sets out on a mission to find proof.
Only, someone is intent on stopping her—by any means necessary.
When her boat is attacked and her research stolen, former Russian Special Forces operative Zak Bychkov and his team at Guardsmen Security step in to provide protection. Carrying survivor’s guilt after a suicide mission killed his entire team, the last thing Zak wants is an emotional entanglement with an opinionated and passionate woman like Alina, especially when she’s been hurt in the past and seems to want to fight him on everything.
But as hostile forces pursue them to the wilds of Norway, the combustible attraction is too much to ignore, no matter how badly they might get burned.
Zak vows to protect the woman who has made his heart beat again, but will it be enough to keep her alive?