DIY Hydrometer

[ggenz]

I need to build a hydrometer for school, does anyone have any ideas for going about doing this?

I could probably make the actual thing out of plexiglass but i dont know how to make it measure anything. i need to have one of those floating pointers (which i could make)but i dont know the exact measurements and that kind of thing.

it needs to read saltwater concentratioins between 1 and 10 percent

any thoughts or ideas would be helpful thanks

[ggenz]

never mind, i found it online, i was making it way too hard, trying to make one of the nice plexiglass ones