In the last five years, alien lionfish, pufferfish, rabbitfish and sea urchins have proliferated in southern Crete. They are part of the 600 alien marine species that have entered the Mediterranean Sea via the Suez Canal. Vibrant imperial debris and afterlives of global shipping, the tropical fishes are transforming ecologies across the sea. In this presentation, I delve into feelings of hope and despair when it comes to these processes. I conceptualize my interlocutors’ apocalyptic mindset and its concomitant ethics (which alarmingly is reflected in current biodiversity agendas) as a form of ‘cruel environmentalism’ to zoom into two rather different forms of cruelty. First, this mindset relies on necropolitics, advocating the killing of migrant species to save native ecologies. In this case, the solution to goes via the belly and 'invasivorism', i.e. the devouring of invasive species. Awareness campaigns inform consumers to “eat responsibly” by putting aliens on the menu. Marine biologists underline that endemic fishes need to cultivate a taste for alien inhabitants, turning invasivorism into a multispecies ‘responsibility.’ Second, this environmentalism is a form of ‘cruel optimism’ because of its futility. At its core, Laurent Berland (2011) explains, a psychological or emotional attachment is cruel when your desire (or the object of your desire) turns into an obstacle for your flourishing. The seascapes my interlocutors yearn for and seek to protect are not only landscapes of the past, they are idealized frozen memories of ecologies that only existed for a sliver of time (Kirsey 2015).