The Ministry of Defence says it will abandon deep-diving experiments which involve inducing decompression sickness in live goats.
The animals were used to see what the likely risk of “the bends” would be following escape from a submarine at varying depths under water.
The information would help crews judge whether it would be safer to abandon a stricken vessel or wait to be rescued.
Animal rights campaigners say the move will “end decades of animal suffering”.
More than 400 such experiments have taken place since 2000.