Pseudoraphis spinescens

About

Pseudoraphis spinescens, called spiny mudgrass or Moira grass is a rhizomatous and stoloniferous aquatic or semi-aquatic perennial grass, with ascending stems forming loose, floating mats in water to 1 m deep or more, or with stems to 50 cm high when not submerged. Moira grass was first described in 1810 by Robert Brown as Panicum spinescens, and subsequently transferred to Pseudoraphis by Joyce W. Vickery in 1950.

Summary from Wikipedia