We discuss the studies of superfast quarks as a new method in probing high-density fluctuations in the nuclear medium. Kinematical as well as dynamical aspects of probing such fluctuations are discussed. Several theoretical models are considered which are based on significantly different underlying picture of high density nuclear fluctuations that generate superfast quarks with x Bj > 1. First, is the convolution model in which it is assumed that fast quarks originate from the nucleon which is in short-range NN correlation. In the second model it is assumed that 2N system is collapsed into the sixquark configuration from which the superfast quark is produced. The third approach considers a situation in which the high density fluctuation is not yet a six-quark system and the superfast quark is generated due to hard exchange of a single gluon between two partons, one from each nucleon. This represents an intermediate stage between the first two models and may correspond to the scenario of evolution of 2N system into six-quark configuration. We compare the predictions of all three models and discuss the feasibility of their experimental verification.