James Messham, from Shoreham-by-Sea, West Sussex, died after an “altercation” on the MSC Virtuosa at around 8.30pm last Saturday.
A 57-year-old man from Exeter, Devon, was arrested on suspicion of murder by Hampshire Constabulary and released pending further inquiries.
The force has now confirmed a second man has been arrested.
A spokesman said: “A 56-year-old man from Richmond, London, has been arrested on suspicion of manslaughter and remains in custody at this time.
“We remain keen to hear from anyone who was aboard the ship, which had departed Southampton around 6pm on Saturday and was still in British waters at the time.”
She cruise ship had left Hampshire for a two-night journey to Bruges, Belgium.
Mr Messham, who operated the travelling show Messham’s Wall of Death, has been described as a “great showman” by friends posting tributes on Facebook.
