Ship Trap Island Descriptive Writing

While I was strolling on the beachfront, I happened upon a bottle under the slowly rolling waves. I picked it up, unscrewed the cork cap, took out the parchment coiled inside, and rolled it out on the fine sand to read the message. It was written in Spanish, but my years of education in the Spanish language had allowed me to effectively decipher it.

To whomever finds this letter, I was one of the sailors aboard the Sanlúcar, the Spanish cargo ship that crashed near the shore of this accursed island: Ship-Trap Island. We were on a cargo run to the port of Southampton after we left Spain, but while crossing near this island, we took a turn to a channel. That channel did not exist, and our boat capsized and I have no memory of the events immediately after. Me and twelve other sailors found ourselves awake in a dark cellar. He periodically came down there to physically train us, and there was an assortment of weights there. He also periodically forced us to run around a ringed trail around his chateau, which was to prepare us for the “game”.
He already took one of my shipmates to play, Carlos his name, and we have not seen from him since. I can only assume the worst: he killed him. As I write this, I am planning my escape from this wretched hive. When I am taken out for the game, I will jump out into the ocean. It will be a far chance, but should I wash up on the shore of the mainland, I will inform the authorities. Should I fail, whoever found this letter should make sure to tell the authorities of whatever land this washes up: take down Ship-Trap