Kadua littoralis is a succulent perennial herb with slightly woody bases. It typically grows with decumbent stems at the base, extending 25–40 cm in length, quadrangular in cross-section when dry, and is glabrous. The leaves are opposite, clustered near the base of the stem, and more dispersed on new shoots. The blades range from ovate to broadly elliptic, measuring 3.5–13.5 cm in length and 1.5–7.5 cm in width. They are fleshy with a glossy upper surface and a dull or glossy lower surface, with entire margins and lateral veins that are impressed on the upper surface. The leaf bases are sessile and slightly connate around the stem, with stipules adnate to the thickened leaf bases, forming a sheath that ends in a fleshy mucro. The flowers emerge on 20–30 cm long scapes, arranged in subumbellate, corymbose cymes that can extend with monochasial branches, featuring pedicels up to 20 mm long. These inflorescences are subtended by broadly cordate to orbicular bracts. The flowers are perfect: a calyx with 4-5 foliaceous, oblong-ovate lobes and a white, salverform corolla with a tube 8–11 mm long. The corolla’s lobes are inflexed in bud, and the nectary disc is present. The stamens, inserted within the corolla tube, have sessile or short-filamented anthers. The fruit is an obconical capsule, measuring 6–10 mm in length and 5–9 mm in diameter, with a firm-fleshy mesocarp that exfoliates when dry, leaving a depressed-subglobose vascular tissue and weakly sclerified endocarp. The seeds are dark brown, peltate to broadly cuneiform, irregularly and bluntly angled, and feature a black papillose surface. These seeds have a well-developed oily endosperm, though sometimes the endosperm is scant or absent. It typically inhabits wet rocky sea cliffs and coastal talus slopes, often within the range of salt spray between 2–6 meters.