One of the first tweets read: "You let your dad down i hope you know that."
Another tweet, from the same Twitter handle, is apologetic.
"I'm sorry mate i just wanted you to win cause its the olympics I'm just annoyed we didn't win I'm sorry tom accept my apology."
Later, the tweets become more aggressive, such as one that said: "I'm going to find you and I'm going to drown you in the pool ..."
Subsequent tweets, spiked with profanity, also take aim at the media and other Twitter users who criticised his posts.
Police said the teen was detained at a bed and breakfast in the southwestern coastal town of Weymouth in the early hours of Tuesday morning, and is currently helping police with their inquiries.
In Britain, tweeting messages considered menacing, offensive or indecent can lead to prosecution.
- AP