溪木贼（Equisetum fluviatile），又名水问荆或水木贼，是多年生植物，一般沿淡水岸边或浅水中茂密的生长。

溪木贼是草本植物，高30-100厘米。茎呈深绿色，直径长2-8毫米，表面光滑，有10-30节。在每一节中，茎上都有5-10毫米长细小及黑色叶端的鳞片叶。很多茎上都有短小长约1-5厘米的枝子，最长的枝子则位于茎的中下部。侧枝幼长，呈深绿色，有1-8个结节，每结节有5片鳞片叶。

溪木贼的纵沟是木贼属中最大的，占了茎部的80%。溪木贼可以于结节位伸缩，而生殖枝及有营养枝的外表相似。

溪木贼可以孢子及从根茎以营养方法生殖。它主要是营养的方法来繁殖，从根茎中长出大部份的嫩枝。在一些枝端上会长出孢子。孢锥呈黄绿色，长1-2厘米及阔1厘米。

The water horsetail (Equisetum fluviatile), also known as the swamp horsetail, is a perennial horsetail that commonly grows in dense colonies along freshwater shorelines or in shallow water, growing in ponds, swamps, ditches, and other sluggish or still waters with mud bottoms. It is a herbaceous species, growing 30–100 cm (rarely 140 cm) tall with erect dark green stems 2–8 mm in diameter, smooth, with about 10–30 fine ridges. At each joint, the stem has a whorl of tiny, black-tipped scale leaves 5–10 mm long. Many, but not all, stems also have whorls of short ascending and spreading branches 1–5 cm long, with the longest branches on the lower middle of the stem. The side branches are slender, dark green, and have 1–8 nodes with a whorl of five scale leaves at each node. The water horsetail has the largest central hollow of the horsetails, with 80% of the stem diameter typically being hollow.