Ryan Photographic - Thalassinidae - Mud lobsters
The family Thalassinidae contains 9 species in the genus, Thalassina.
They are distributed in the mangrove swamps of the Indian and Western Pacific oceans where they are important "ecosystem engineers". Mud lobsters dig deep burrows which aerates the normally anoxic mud and builds mounds that rise above the normal high tide mark. This allows plant growth and provides refuge for other mangrove dwelling species. Check this out for more details. The family was revised in 2012 by Katsushi Sakai and Michael Turkay.
A Wikipedia entry on the genus suggests "the meat is bland and it is never very popular." Tell that to the Fijians where "mana in miti" is a local delicacy (mud lobster tail flesh marinated in lemon or lime juice and then mixed with chili, onion, tomatoes and coconut milk - or some combination thereof).
Thalassina anomala Mangrove mud lobster
Thalassina anomala, mangrove mud lobster, Suva, Fiji. Although this animal looks "cooked" it is thoroughly alive but submitted to the indignity of having mud rubbed off it. At least it wasn't eaten.
Thalassina anomala, mangrove mud lobster burrows