The near-equatorial region is importantly different from other ocean areas: it acts as a barrier for large-scale meridional circulation, because the strongest currents are directed East-West, and it shows weak interior mixing despite large internal wave shear. All seems related to a change in importance of the vertical 'inertial' component of the earth's rotation. As rotational effects dominate large-scale ocean motions through a geostrophic balance, they become negligible at the equator. Here, deep-ocean observational evidence is presented of hitherto neglected rotational effects. It is demonstrated that when the equator is approached near-inertial internal wave motions very suddenly rather than smoothly change polarization from near-circular to near-rectilinear within half a degree across latitudes ∣$varphi$∣ = 1.5 ¿ 0.5¿. At the same latitudes sudden transitions are observed of large-scale kinetic energy and small-scale density stratification variations. Understanding the above requires a non-traditional approach in which the horizontal component of earth's rotation is considered.