East Asian naval defence primarily rested on the possession of a riverine/coastal navy sufficient to deter (usually nomadic) enemies, but there were also other ways where a land-based force could deter naval forces.
First, there's the standard 'chain stretched across the water' tactic, where a large chain blocks a waterway and, at the very least, slows down an invading naval force.
Then there's sea walls, where defenders would built a wall parallel to the coast, and deny enemies a safe place to land. This tactic was most notably used in the Japanese defence against the Mongol invasions.
An army facing a fleet close to shore (or hemmed in by riverbanks) could use fire incendiary arrows at an enemy. With the development of catapult technology and especially the introduction of the counterweight trebuchet with the Mongols (previously the Chinese only had traction trebuchets), land-based trebuchets started to be used against naval forces, throwing either rocks, primitive grenades or naptha bombs. This tactic was viciously effective in decimating the Southern Song navy during the final stage of the Mongol conquests.
Finally, defenders could put large iron stakes in coastal/riverine shallows or in tidal areas, drawing the ships in until they got stuck on the stakes and became sitting ducks for the defenders. East Asian ships were generally flat-bottomed with no keel, so this tactic was quite effective against them. The Annamese used this to great effect in repelling the Mongol invasions of their country.
