Tom, 18, received an abusive message yesterday after he and his GB diving partner, Pete Waterfield, came 4th in the synchronised 10 metre platform at the Olympics.
The vile tweet read: "You let your dad down I hope you know that."
Tom's beloved father Rob died last year after a long battle with brain cancer. He was 40.
The teenage sports star is refusing to let the cruel tweet upset him, though.
"Thank you everyone for all your support before, during and after the synchro, the atmosphere was incredible! Now focussing on the individual," Tom tweeted.
Before the Olympics, Tom had told the BBC: "Winning a medal would make all the struggles that I've had worthwhile.
"It's been my dream since a very young age to compete at an Olympics. I'm doing it for myself and my dad. It was both our dreams from a very young age.
"I always wanted to do it and Dad was so supportive of everything. It would make it extra special to do it for him."
Dorset Police confirmed they had arrested a 17-year-old boy at a guesthouse in Weymouth, close to where the Olympic sailing events are being held.
A spokesman for the force said: "A 17-year-old man was arrested by Dorset Police in the early hours this morning at a guesthouse in the Weymouth area on suspicion of malicious communications.
"He is currently helping police with their inquiries."
Scroll through our gallery below of Tom Daley's behind-the-scenes Olympic photo album.
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