Few of us realise that the oceans of the world are a relatively untapped reservoir of new natural product-derived medicines to combat the many diseases that plague humanity. We explore the role that an unremarkable sea snail and sea squirt are playing in providing us with new medicines for the alleviation of chronic pain and cancer respectively. This article not only highlights the challenges of sustainably harvesting populations of marine invertebrates for their natural products to fuel the drug discovery pipeline but also describes innovative ways in which some of these challenges have been overcome. Highly biodiverse and fragile marine ecosystems, like their tropical rainforest counterparts, are potentially the pharmacopoeia of the future and must be rigorously conserved. (Contains 4 figures.)