gRomoZeka offers some suggestions:

Заключенное в оковы
Should this be в оковах (prepositional), or is заключить considered in this context to express "logical motion", as in сажать/посадить в тюрьму (accusative)?

В замерзшем заливе
"Гуантанамо"
To me it sounds strange to use the word залив ("bay") here. Because metaphorically, the poem refers neither to the actual Bahía de Guantánamo (i.e., the body of saltwater), nor to the U.S. military installation that's officially called "Naval Station Guantanamo Bay" -- but to the "Camp X-Ray" prison that was built within the territory of the base after 9/11. Since the base itself is often informally called "Guantanamo" or "Gitmo", and both of these terms are sometimes used in the media in reference to "Camp X-Ray", might I suggest either в замерзшем "Гуантанамо" or в замерзшем "Гитмо"?

P.S. Я свидетельствую о том, что сама база "Guantanamo Bay" ни в чём не является тюрьмой -- ведь в детстве я провел два счастливых года в детском саду и первом классе на "Гитмо"! Значит, следует не путать залив, базу ВМФ, и тюрьму. ("I'll bear witness that the base itself is in no way a prison -- after all, as a kid I spent two happy years in kindergarten and first grade at Gitmo! Thus, one ought not confuse the bay, the Naval base, and the prison.")