I was just wondering if someone could help me with a buoyancy question. I'm trying to calculate the volume of water displaced by my river rapids boat depending on the depth it is submerged. The rubber section, which will be partly submerged, is bascially a dognut (torus) with the inside filled in. The distance from the centre of the tube to the centre of the torus, R is 3.6m and the tube radius, r is 0.4m. Its depth is 0.8m. I know that the volume of a torus = 2 (pie^2) x R x r^2, however my problem has the inside section included as well and I need to know how its volume increases with height. Any help would be much appreciated, thanks.