A sanitary doctor, part-time combat swimmer, deals with acoustics, ventilation and lives for his own pleasure. A favorite of women, a classy specialist, Igor receives a business trip to Pakistan to perform a strange task: reducing the echo in a mosque, and happily leaves for a business trip abroad, not knowing that he is being developed by the KGB. Having successfully reduced the echo in the mosque, which was simple at first glance, Igor was faced with the problem of returning to his homeland. Using the routes of smugglers, illegally, Igor returns home and again comes to the attention of the KGB. The committee members are going to use Igor as a one-time agent in order to retrieve an ancient artifact from the bottom of the Aral Sea for scientific research by the special services. Only a trained swimmer from a depth of more than thirty meters, without the use of technical means, can get an artifact that is so necessary for special services. Work in the sanitary and epidemiological station, acoustics, Pakistan, smugglers, the work of special services, the islands of the Aral Sea and of course underwater adventures are intertwined in the new novel of the famous writer Anatoly Sarychev, who lies in front of you.