This chapter analyses the treatment of animals in sea warfare under extant international law and it assesses the adequacy of these norms for the protection of animal welfare. The welfare of marine animals is threatened by warfare in various ways. Individual marine mammals, such as dolphins or sea lions, are trained to take part in hostilities. Other sea life suffers, whether directly or indirectly, the repercussions of hostilities. In the context of prize law, animals could in some cases qualify as contraband goods, susceptible to seizure when on board neutral vessels heading toward enemy ports. It is concluded that the law as it stands today provides neither optimal protection for animals considered as a constitutive part of the marine environment nor for animals in themselves considered as sentient beings. The chapter formulates recommendations for the progressive development of the law, including the creation of a sui generis status for sentient animals, the regulation of military sonars and the establishment of protected marine zones where no combat activities whatsoever should take place.