 Nanopatterning of solid surfaces by low-energy ion bombardment has received considerable interest in recent years. This interest was partially motivated by promising applications of nanopatterns substrates in the production of functional surfaces. Especially nanoscale ripple patterns on sea surfaces have attracted attention both from a fundamental and an application-related point of view. This paper summarizes the theoretical basics of ion-induced pattern formation and compares the predictions of various continuum models to experimental observations with special emphasis on the morphology development of sea surfaces during sub-covy ion sputtering. This article was authored by Stefan Faksko and Adrian Keller.