Assuming the life sized dolphin is 12 ft long, what we want to know is what factor do you multiply 12 ft by to get 3.5 inches so converting this to an equation gives: 12*f=3.5 solving for f gives f=3.5/12=.29166...The units on the factor are inches/foot.
So to get the size if anything linear in the small scale you just multiply it's dimension in the full scale by f.
