In this Letter, we demonstrate high-energy and high-peak-power nanosecond pulse generation aiming at the 2.94 μm water absorption peak, from a 980 nm diode-clad-pumped actively Q-switched Er3+/Dy3+ codoped fluoride fiber oscillator, for the first time. Operating at the 2943 nm wavelength locked by a diffraction grating in a Littrow configuration, stable Q-switching with the shortest temporal width of 41 ns has been obtained at a low repetition rate of 100 Hz. The maximum pulse energy of 108 μJ and peak power of 2.48 kW are primarily limited by the thermal damage of the bare fluoride fiber facet for pump coupling, and represent the records of pulsed fiber oscillators around 2.94 μm, to the best of our knowledge. This advanced nanosecond laser source provides an optional promising tool for laser medical applications.