企嶺下紅樹林是香港最大的紅樹林之一，像汀角的紅樹林一樣被選為具特殊科學價值地點（SSSI），紅樹林的部分更為吐露港增色不少。與其他由粉質和泥質底物組成的紅樹林泥灘不同，這裡的基質由鵝卵石和沙子組成。幾乎所有在香港有記錄的紅樹林品種及相關植物都可以在企嶺下紅樹林找到，包括稀有的木欖和不常見的欖李。典型的成帶現象亦出現在企嶺下紅樹林：秋和桐花樹均佔據了大範圍的海面部分，秋通常生長在較泥濘的基質上。在較近陸地的範圍，可以找到白骨壤丶老鼠簕丶欖李和海漆。在紅樹林的背面生長著不同的植物，其中包括黄槿丶假茉莉丶露兜樹和其他海岸植物，可是這樣的海岸生境愈見稀少。西貢附近的紅樹林群落，是常用進行生態研究和實地考察的地點之一，位置西獅子會自然教育中心更會定期舉辦導賞和展覽活動，教育大眾生態保育的重要性。紅樹林的泥漿也對不同的生物十分重要，這些泥漿為有毒的無脊椎動物提供棲息地，而無脊椎動物又為鳥類和魚類等較上層的捕食者提供食物，企嶺下紅樹林也曾發現新的無脊椎動物。

This mangal is one of the largest stand of mangroves in Hong Kong. Like the mangal in Ting Kok SSSI, it is the remain of the mangrove once flourishing the Tolo Harbour. Unlike other mangals which consist of mainly silty and muddy substrate, the substrate here also includes sand covered with cobbles in many places. Almost all mangroves and their associated plants recorded in Hong Kong can be found here, including the rare Bruguiera gymnorrhiza and the uncommon Lumnitzera racemosa. The latter is rather common at the back of this mangal.
A clear zonation pattern can be observed: Kandelia candel and Aegicerus corniculatum dominate the seaward part of the community with the former normally grows on more muddy substrate. At the more landward part, Avicennia marina, Acanthus ilicifolius, Lumnitzera raccemosa and Exoecaria agallocha can be found. At the back of the managal is a well developed strip of mangrove associates including Hibiscus tiliaceus, Clerodendron inerme, Pandanus tectorius and other shore plants. Such well developed shore back community is now becoming rare.
The mangal community, especially the part near Sai Kung, is one of the favourite sites for postgraduate research (e.g. Leung 1987) and ecological field trips. The site is also a study place for courses organized by the Field Study Centre of Education Department at Sai Kung.
The mud flat outside the mangal is also of biological importance. It supports nermous invertebrates which in turns provide food for larger animals such as birds and fish. Invertebrate new to science have been found here (Hirayama 1992, Mackie 1991).