Plot hole: Saint Marie is an island with an astonishing homicide rate, but even considering that, with an a missing person and a phone call reporting a stabbing at the boat of a notorious belligerent drunk, with the same person called by name as the culprit, it's quite inconceivable that in a relatively small town like Honore nobody looked for Newton Farrell and questioned him all night - especially being so easy to find, or even checked the boat. Instead, they are surprised by the bleaching of the deck the day after, proving they did not even look for a moment during the night.
Continuity mistake: Addison Patrick pulls out of his pocket a bag with the coins. A string dangles off his palm, but when he hands it to Florence, the strap has been pulled up. (00:30:20)
Revealing mistake: Dwayne supposedly swapped the rum with Humphrey, but if you pay attention during the time when JP hands them the glasses, it simply does not happen. (00:26:00)
Continuity mistake: Goodman calls it a day and mentions the stag party. Dwayne lays out on the desk three pair of handcuffs; the leftmost (the first he put down) is apart from the others, but when the lube comes into play, all three are clustered together. (00:22:35)
Continuity mistake: Florence puts on the table the knife sheath; it is laid out with the ends of the belt apart, but when Newton Farrell answers, they are joined together without anyone having touched it further. (00:20:30)
Continuity mistake: Humphrey found the cigar butt inside Newton's ship. He goes with his ever-smiling sidekick to interrogate him, finding him in asleep with a flask of booze between his hands. Cut, and Roger Griffiths' hands are on top of the flask instead than the bottom. (00:20:10)
Continuity mistake: Florence finds the divorce papers and calls Humphrey's attentions on them saying "Sir..." There is a paper sheet leaning by a corner on the laptop's right side. When the tabletop is again in frame (when Humphrey puts the coin back in the safe) the papers are arranged differently. (00:18:30)
Continuity mistake: The police are inside Tosh's boat, and Naomi Walker pokes downstairs to tell them that all his stuff is there and to help themselves. She has both hands on the manhole, which becomes just the right hand at the first cut. (00:17:25)
Continuity mistake: Humphrey grabs the ashtray in the boat; the cigar butts are placed differently on it between shots. (00:17:25)
Other mistake: In Naomi Walker's flashback when she gives Goodman her recounting of the evening, she gets the call from her husband when the phone is on the table - she got it with the phone in mid-air as she was standing already, instead. (00:11:10)
Continuity mistake: Sam Walker is holding back his dad Tosh, pulling him apart from the rival Newton Farrell. When Tosh snarls "Get away from my boat", his son has his left hand on his shoulder, but it's behind his back in the intermediate reverse shot. (00:01:25)
Other mistake: JP tells the others that his fiancée cooked him a great meal for the two-month anniversary the other night. Suddenly, the three months anniversary is coming up and he proposes - but just a day passed.
Character mistake: Matt Holt's profile contains a very minor typo (missing space between 'mother' and 'was') and lists his age as 20, while he's still 19, having his birthday in August. The biggest mistake though lies in the fact that it processes a request dated 29 of April; it should be the 30th, just like Gary's. (00:26:10)
Other mistake: It is never clarified why the victim paid his brother; besides that, the bank statement has the date of April 29 and most facts point at the date being the one the episode is supposed to take place at. The investigative report though refers to a meeting happening in January - would hardly be something the aggressive legal team of the even more aggressive chef would keep on their desk for 3 months.
Continuity mistake: Classic mistake of the series (happens at least in a couple episodes per seasons); the Detective Inspector writes down names on the whiteboard, but they are written in different penmanship in close-up compared to the wider angles. In this particular case, the detail that is most telling is how Humphrey puts a little underline on some of the names, which is at very obviously different distance for the victim and the pastry chef. (00:14:00)
Continuity mistake: The DS, DI and Officer Myers are looking at JP when Dwayne says that there's "trouble in paradise." The bottles of beer turn in their hands in between shots. (00:50:20)
Continuity mistake: When Dwayne informs his bosses that they used to call him "The Shaquille O'Neal of Saint Marie", he is suddenly leaning again against the bar post, he was not before the cut. (00:50:05)
Continuity mistake: It's time for a motive for Kim Sweeney, and the inspector and DS go to interview her. She is in her bed, surrounded by used paper tissues, which change position between shots. (00:33:45)
Revealing mistake: Florence and Humphrey are reading the article about the young Dexter Allen from the Hackney Gazette. Behind the article, Florence has her mail open. Amazingly enough, the names of the people she received mail from (Joshua, David, Faye, a Customer service) are the same ones as the victims in She Was Murdered Twice, season 4 episode 7 when one of the suspects opened it from a public computer. (00:30:45)
Other mistake: Dwayne goes through the deleted text messages in Robert's phone. The messages have as dates "Thursday 19" and "Saturday 21st." Given that the year is 2016, the dates are compatible with the month of May, but the episode is set on April 29 - it's the date on the police report for both Matt Holt's background check and the bank receipt Gary Holt shows. (00:19:25 - 00:29:45)
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.