The photocatalytic activity of layered perovskite-like oxides in water splitting reaction is dependent on the hydration level and species located in the interlayer slab: simple or complex cations as well as hydrogen-bonded or non-hydrogen-bonded H₂O. To study proton localization and dynamics in the HCa₂Nb₃O₁₀·yH₂O photocatalyst with different hydration levels (hydrated—α-form, dehydrated—γ-form, and intermediate—β-form), complementary Nuclear Magnetic Resonance (NMR) techniques were applied.1H Magic Angle Spinning NMR evidences the presence of different proton containing species in the interlayer slab depending on the hydration level. For α-form, HCa₂Nb₃O₁₀·1.6H₂O,1H MAS NMR spectra reveal H₃O+ . Its molecular motion parameters were determined from1H spin-lattice relaxation time in the rotating frame (T_1ρ) using the Kohlrausch-Williams-Watts (KWW) correlation function with stretching exponent β = 0.28: E_a = 0.210(2) eV, τ₀= 9.0(1) × 10−12 s. For the β-form, HCa₂Nb₃O₁₀·0.8H₂O, the only1H NMR line is the result of an exchange between lattice and non-hydrogen-bonded water protons. T_1ρ(1/T) indicates the presence of two characteristic points (224 and 176 K), at which proton dynamics change. The γ-form, HCa₂Nb₃O₁₀·0.1H₂O, contains bulk water and interlayer H+ in regular sites.1H NMR spectra suggest two inequivalent cation positions. The parameters of the proton motion, found within the KWW model, are as follows: E_a = 0.217(8) eV, τ₀= 8.2(9) × 10−10 s.