Diffuse galaxies with detection in ALFALFA H I (top row) and VESTIGE Hα (bottom row). The color composite images are from the NGVS u, g, and i bands. The dashed yellow circles show the ALFALFA beam (3.5′ diameter). The Hα images (bottom row) were smoothed with a Gaussian kernel of σ = 3 pixels, and the image color contrast range is from an Hα surface-brightness level of 10⁻¹⁸ to 10⁻¹⁴ erg s⁻¹ cm⁻² arcsec⁻².