They don't sink. The largest two or three pieces are tree roots. They are about 43 x 30 x 25cm. They are quite large. They are all interesting shapes. How about using them for reptile or insect layouts, or for paludariums? They have been soaked in water for a while and then dried thoroughly. I will check them carefully before shipping, but there may be small insects mixed in. Thank you for your understanding. ADA ADA Horn Wood Aquarium Terrarium Vivarium Paludarium Insects Reptiles