Here is the full list of all 25 Hotel Transylvania 3: Monsters Overboard trophies - there are 7 bronze, 10 silver, 7 gold and 1 platinum.
Defeat the Cruel Crustacean and retrieve the second part of Neptune’s Compass
Defeat an enemy with the impact from a thrown Frankenimpa.
Rescued Frankenstein.
Unlock half of all Impa Portals.
You’ve safely retrieved an object from an angry Giant Clam.
Defeat the Fiendish Flower and retrieve the first part of Neptune’s Compass.
You’ve collected the first of many treasures.
Rescued Wayne.
Defeat a Coconut Crab while it’s stunned.
You’ve defeated 5 enemies in a single night.
Collect 5 Imparite stones in a single night.
Unlock the third Impa Portal.
Complete the tutorial and meet up with Ericka.
Congratulations! You’ve done all there is to do in Hotel Transylvania 3: Monsters Overboard!
Rescued Murray.
Defeat the Dastardly Dragon and retrieve the final part of Neptune’s Compass
Collect half of the Treasures hidden in the Lost Islands.
Collected every single Treasure hidden in the Lost Islands.
Have 5 of each Impa type at once for more than 5 seconds
Unlock every single Impa Portal.
Have 30 Vampimpa at once for more than 5 seconds
Defeat any enemy other than a Feeble Flower with nothing but a single Wolfimpa.
Use Mummimpa’s Magic Sand to block the smell trail from a Stinkbulb.
You’ve successfully liberated 3 objects from Giant Clams.
Hit an enemy with a ricocheted Mummimpa.