Though the main task of neutrino telescopes with volume about 1 km^3 (IceCube, Baikal-GVD, KM3NeT) is the search of neutrinos of astrophysical origin, they give a good possibility for investigations of atmospheric muons with energy more than 100 TeV (VHE muons). Measurements of the energy spectrum and angular distribution of such muons give information about primary energy spectrum and mass composition at energies around the knee and also on muon generation processes. In this paper, in order to evaluate the possibilities of studying the spectrum of muons of very high energies by giant underwater (ice) setups, simple analytical calculations of the expected spectra of cascades are carried out. Influence of characteristics of primary cosmic rays and model of interaction on results of muon energy spectrum measurements is discussed.