padi IDC dive theory – Physics

Q17
Underwater object appear _____ and _____, but a phenomenon called visual reversal make them appear ____
c.) Larger / closer / further
 
Q18
I have a balloon which has a volume of 2 litres at 30 meters. What will its volume be at 20 meters?
a.) 1 liter
b.) 4 liters
c.) 0.66 liters
d.) 2.67 liters