Interesting that the responses are world wide as if the aggressiveness of a mantis shrimp is something new.
I do not know the world wide distribution of mantis shrimp but I do know we have them in California.
Several generations ago the flats at Emerald bay, Catalina Island was known for its densely population of these little critters.
Often we would dive there and hunt for them.
Equipped with a short stick as a prod and an apple also on a short stick as a aggressor target we would locate a hole, prod the hole with the stick until the Mantis Shrimp appeared, place the apple in from of the mantis as if it was the antagonist. The Mantis Shrimp would aggressively repeatedly strike the apple, not once but many many times.
After the combat was finished we would examine the apple which had multiple wounds as deep as a half inch or more.
They were a small critter that you didn't want to mess with. However, on a number of occasions they were taken with a well gloved hand to relocate to another area for combat with another Mantis Shrimp.
The early underwater California rendition of the Mexican bull fight.
Now you know how it is done. Max you can make a movie and Dr. Bill can write a story about the Mantis Shrimp.
SDM