The urethra opens on the underside of the glans instead of at the tip. In an intact boy, severe hypospadias would present as an incomplete foreskin, like a hood, and the peehole underneath the head. You would notice severe hypospadias.
In an intact boy, a very mild case would probably go unnoticed until he became retractile. A more moderate or severe case(that would warrant intervention) you would see a physical abnormality from the outside (without retracting)