This chapter highlights the nature of karstified coastsKarstified coasts and the related coastal hydraulicsCoastal hydraulics of the oceanic islands. Limestone dissolutionLimestone dissolution, tidal pumpingTidal pumping, seepage linesSeepage lines at the upper limit of HTL, water layer weatheringWater layer weathering, evaporation, precipitation, calcificationCalcification, and bio-encrustationBio-encrustation processes are explained, and their spatio-temporal variations are demonstrated in this section of the study. A schematic classification of karstified coastsKarstified coasts is documented for the South Andaman Islands in this chapter. Coastal karst featuresKarst features are identified in the shore cliffsShore cliffs and shorefront platforms of the islands. Sea cavesSea caves and island interior cavesIsland interior caves are explored with monitoring geomorphological features to explain the valley as a base-level control factor in the islands. Extensive beach rock formation sites with sandy limestones, shell limestonesShell limestones, and conglomeratic debrisConglomeratic debris limestones are found in the high tide zone and mid tide zone of the islands. The island-front seepage zones with dissolved carbonic acidsDissolved carbonic acids played an important role in the cementation of beach deposits at higher sea levels. Sea levels, inter-annual variations, tide levels, storm surge levels, swell waves, and tsunami waves, as well as the discharge of spring waters from the shore cliffsShore cliffs, are considered as part of coastal hydraulicsCoastal hydraulics for the promotion of the karstification process on the shore platforms. Phytokarstic featuresPhytokarstic features are more prominent in the algae-encrusted biofilm surface on the limestone beds of the island coasts.