A drift bar is lowered into a well. The drift bar has a density that is less than a density of a wellbore fluid residing in the well. A tubular is lowered into the well below a surface level of the wellbore fluid residing in the well. The tubular defines an inner bore having an inner diameter that is greater than an outer diameter of the drift bar. The drift bar is positioned to pass through the inner bore of the tubular as the tubular is lowered into the well. After the tubular is positioned below the surface level, an absence or presence of the drift bar floating at the surface level is detected. An absence or presence of a restriction in the inner bore of the tubular is determined in response to detecting the presence or absence, respectively, of the drift bar floating at the surface level.