The Chupacabra is a Mexican folk legend (goatsucker) monster who is known to drink the blood of goats. This is why the bartender gives him a goat in a glass when he asks for a drink.
In the short film Puppy!: A Hotel Transylvania Short (2017) Released a year before this feature film, Mavis can be seen reading the travel brochure for the actual cruise ship from Hotel Transylvania 3, months before it was officially revealed to the public.
Frank says the woman, with whom he tries to set Dracula up, is his "right arm's cousin". This was also what Johnny said in Hotel Transylvania (2012) when he was trying to convince Frank that they were related.
The VFX team had to build all the individual ships that were in the Bermuda Triangle because they wanted a believable structure when being stacked.
If you look closely during the Bermuda Triangle sequence, you may spot several actual famous boats that allegedly disappeared in the mysterious location.