Mixed Marsh beetles (family Scirtidae)
 are a small group of aquatic and semi-aquatic beetles found throughout the UK. Around 30 species have been recorded, typically inhabiting wetlands, ponds, marshes, ditches, slow-flowing streams, and other damp habitats. The larvae are aquatic, feeding on decaying plant material and microorganisms, where they play an important role in nutrient recycling. Adult beetles are usually small, soft-bodied, and often found on waterside vegetation. Although inconspicuous, Scirtidae contribute significantly to freshwater ecosystem health and biodiversity.