Crayfish are very shy, hiding during the day because most are nocturnal animals. A main reason why they are very rarely seen.
The more it pleases one, if one can accompany a cancer over months, and observe. Not in the aquarium, but in our bay in Sahl Hasheesh.
This is what happened to the mantis shrimp / Stomatopoda.
We noticed an unusual small shallow in the sand field at 10 m depth, with a hole of about 8 -10 cm and a strange edge.

As it turned out, the dwelling of a mantis shrimp.
This type of crab digs a branching tunnel system in the sand, where they stay protected until they go hunting at night.
Our mantis shrimp, fortunately for us, also shows up during the day from time to time.
He does not leave his protective den, but only comes out of his hole as far as he can to visually survey his surroundings.
You can clearly see how he does this telescoping similar eyes.
The vision of mantis shrimp is highly developed. Their eye is tripartite in order to simultaneously capture optical impressions on three different planes and thus process them into a whole. As a result, the pupils in the eye are constantly moving back and forth. This is a unique form of visual perception in the animal species.

What we also observed is that when it retreats into its den, it uses its tentacles to work and shape the sand around its hole so that there is the protective rim around the entrance.
All this I was able to photograph and also film. (Here is the link to the film at YouTube)
While researching am, what exactly kind of species our mantis shrimp is I came across a lot of material. So now I know that there are over 400 species. Divided into the two groups butterflies and spearers. Dies auf Grund ihrer unterschiedlichen Art ihre Beute anzugreifen und zu erledigen. Der Speerer ersticht und der Schmetterer erschlägt seine Beute.
Based on similar pictures and descriptions, I suspect that our mantis shrimp is Lysiosquilla scabricauda. I assume because according to the description in the marine encyclopedia the Red Sea is not listed as a habitat. Fact in any case is that it is a mantis shrimp.
Fotos: Johann Vifian
Quellen:
https://www.meerwasser-lexikon.de/tiere/9291_Lysiosquilla_scabricauda.htm1
https://www.biologie-seite.de/Biologie/Lysiosquilla_scabricauda