What are the motifs in Pacific Vortex by Clive Cussler?

The value of friendship is a recurring idea. When Pitt devises the scheme to ditch the C54 in the ocean and put a crew aboard the Starbuck, he doesn't ask for an available pilot and diver. He calls on his childhood buddy, Al Giordino to join the mission. In this case, friendship implies not only trust and knowledge of how the other thinks and acts, but also knowing the other's actions and limitations. When Giordino saves Pitt's life and finds a safe cave for them, they are both injured with one air tank between them. Do they head to the surface? No, they work together to explore the caves.