The thrills of piloting jets, surviving in outer space and running an atomic submarine baze great appeal for this author --but being a realist, Mr. Lent is also intensely interested in the rigorous training associated with these highly skilled professions. In his new book on basic training at the Navy's submarine school in New London, Connecticut, he enlightens the young masculine audience on the full program offered there and he provides would be submariners with a vicarious taste of what basic training entails. Through Jim O'Hara a fictional character the daily grind takes on vitality. Jim describes life at camp in a letter to his friend Buzz, then he goes on on survive the weeding out process and to meet the physical demands of such rigors as the Escape Training Tank and the intellectual challenges of classwork. He graduates from the ""guppy"" subs to the imposing polaris subs and winds up at the top of his class. Mr. Lent's purpose in introducing a fictional character is to make highly technical information more readable. Though he achieves this, he also a less desirable by-product. Jim O'Hara and his friends are undeveloped characters, flimsy and shallow against the thoroughly realistic, rugged setting of the Naval school.