A plunging ranula is a mucous extravasation cyst appearing as a swelling in the submental and submandibular regions. We describe a rare case of massive plunging ranula involving multiple tissue spaces. A magnetic resonance imaging scan revealed the true extent of the lesion and its relationship to the surrounding structures. Other imaging techniques and diagnostic tests are discussed. The unusual course of events following surgical excision of the offending sublingual gland is presented. The relevant literature is reviewed.