Cooperative hybrid automatic repeat request (C-HARQ) scheme based on multi-hop relaying has been adopted as an efficient strategy in underwater acoustic sensor networks (UASNs) to extend network coverage and to enhance the performance by utilizing spatial diversity gain. In this letter, we develop a stochastic model for multi-cluster transmissions in UASNs, considering the underwater-specific characteristics such as frequency-dependent signal attenuation, acoustic spreading, multi-path fading and underwater noises. From this generalized stochastic model, we derive accurate analytical expressions to analyse the end-to-end packet error rate (PER) and energy efficiency. Analytical results demonstrate that the C-HARQ scheme can significantly improve the performance of UASNs, especially with the increase in number of relay nodes. Analytical results are corroborated with extensive simulation studies.