This physics video tutorial provides a basic introduction into specific gravity which is a ratio of the density of an object relative to the density of a fluid such as water.
Density Problems: https://www.youtube.com/watch?v=9CKDQE35qXQ
Specific Gravity: https://www.youtube.com/watch?v=ZcJGFZt-NO4&t=1s
Sink or Float: https://www.youtube.com/watch?v=4fwZM6cqyzk&t=1s
Intro to Pressure: https://www.youtube.com/watch?v=kkq8ruV8_Jw&t=1s
