I like this idea. According to my calculations, an iron block is 4,096 cubic pixels (all pixel sizes are with default minecraft textures). All weight comparisons are for exactly 1 block. An iron ingot is 120 cubic pixels. Therefore, 9 iron ingots are 1,080 cubic pixels. If my math is right, an iron block is 3/4 air and 1/4 iron. According to the results, an iron block is only 1.9685 times heavier than water. With similar math, a gold block is only 4.825 times heavier than water. A diamond is 174 cubic pixels, although that is only an approximation since I split up the gem into 2 square pyramids and a rectangular prism. If a diamond is 174 cubic pixels, then 9 diamonds are 1,566 cubic pixels. Around 38% of a diamond block is diamond, the remaining 62% is air. Therefore, a diamond block is 1.338134765625 times denser than water. All wood planks are 0.9 times denser than water. Stone and Sandstone is 2.65 times denser than water (taken from the density of Andesite, Granite, and Basalt, the 3 most common rock types in Earth's crust). Air's density would be counted as 0 since you would need a gargantuan boat for air mass to make a difference. Stone bricks weigh 2.6 times more than water. Silverfish blocks weigh 1.3 times more than water. Wool weighs 1.31 times more than water, but it changes to 1.81 times more than water if it is touching water. Lava weighs 2.5 times more than water. A flowing lava block weighs 3/4, 1/2, or 1/4 as much as a source, depending on how thick it is. Lapis Lazuli is 2.8 times denser than water, therefore a block is only 0.7 times denser than water. That would give lapis lazuli a major use, a strong, solid hull that floats higher than wood. Glass and obsidian is 2.6 times denser than water, TNT is 1.654 times denser than water (as far as why you want that on your vessel, I don't know since a direct hit by a cannonball lights the fuse). All non-opaque blocks have a density of 0 times that of water. A bed's weight is 1.4 times that of water.
I think I typed enough, I will let others finish the list.
It's been almost a year, and Notch isn't even working on Minecraft anymore. xD
I hate how all these great suggestions just rot away to nothing. Jeb should hopefully listen to the public a bit more and implement these ideas into the game. :/
We did get the zepplin mod, though. That proves the modding community is capable of doing it themselves. The API is comming out eventually and it should make things easier.
Rollback Post to RevisionRollBack
Mostly moved on. May check back a few times a year.