Well my lungfish has been playing with the substrate in his new tank as its quite deep, which hes never done before and ive got back home to find that hes completely burried his head
hehe...mine does this all the time. i saw a lung in it's natural habitat on tv doing this in mud so i replaced his gravel with sand and now he spends a few hours a day with his head buried in the ground. he sprays sand out his gills too. it's pretty cool.