I noticed that when the suggestion that the US might offer to release the five Iranians it arrested in exchange for the sailors, the sailors were referred to as captives rather than hostages. Presumably to avoid referring to the Iranians who've been banged up by the Americans as "hostages".

There's no reason to think that the Iranians are at all likely to kill the sailors. Their biggest risk is being killed in some daft rescue attempt or military reprisal, in yet another variety of death by "friendly fire".