Next, the user probably wants information on where to watch it. Since Horriblesubs is a group, they might release it on anime platforms like Crunchyroll, but sometimes they have their own methods like torrents or direct links. However, I should be cautious about linking to unauthorized sources. The user might need guidance on how to legally access the episode.

The user might also want to know about the episode's significance and themes. Episode 590 deals with themes of freedom, humanity vs. beastiality, and the struggle of the Fishman characters. Highlighting character development in characters like Brook, Chopper, or even new characters introduced in that episode could be important.

Lastly, community reactions and reviews. If there are any forums or sites where fans discuss the episode, that could be helpful to mention.

Also, the user might want release dates. Horriblesubs tends to release episodes quickly, maybe even same-time as official releases or slightly ahead. I should mention the date they released it and compare it to official schedules if possible. But I need to verify if 590 was already released. Let me check: One Piece is ongoing, and episode 590 was released in 2010. So maybe the user is looking for a retrospective or how to access it now.

Additionally, the release format: whether it's a standard dub or a special version. For example, did Horriblesubs do any special editions or remastered dubs for this episode?

First, I should check the episode details. Episode 590 of One Piece is titled something like "The Deep-Sea Trench: The Sea of Darkness" or similar. It's part of the story where the Straw Hats are on Fishman Island. Key events might include the battle against the Whalenoids or encounters with other characters. I need to confirm the title and main plot points.