currently I am doing coursework where I am dropping a buoyant ball from different heights above a water tank into the water tank. I am then measuring the depth. I lack results so I was wondering if I plotted a graph of height vs depth - would it be a straight line? I think it is because I can say that 1/2 mv^2=fd where force is the buoyant force of the ball which will be constant. But I'm just worried that there's something I've missed out here - so yeah would the graph be a straight line??

^^^ missed something out I meant to put mgh instead of 1/2 mv^2...
id assume h/d = f/mg... and f/mg is constant

Depth of What?

Depth of tank cannot change, so please clarify.

How deep the ball goes... not the depth of the tank. I measure the height above the tank I drop the ball... then I drop the ball film it - freeze frame it to see how deep below the waterlevel the ball gets.

One other thing to consider. The ball has another force on it that consumes its energy. Drag. If you had a ball with neutral buoyancy, it would slow down from drag in the water. And finally come to a stop and just hang there. That drag will be proportional to velocity in the water. So a plot of depth of penetration in the water versus the height it was dropped from, shouldn't be a straight line.