How do you measure the deck area?
Don't price the water surface as deck. For several rectangles, work out each area and add them. Subtract an opening only when it sits inside the area you measured. Curves, level changes, stairs and irregular edges need a proper site measurement, not a guessed rectangle drawn around them.
What does a worked example look like?
A measured 40 ft by 25 ft rectangle is 1,000 sq ft. At an illustrative rate of $7 per sq ft, which you would replace with your own, that line is $7,000 before tax and any work listed separately. The $7 only shows the multiplication. It is not a recommended or researched market rate for pool decks.
What should the rate include?
A unit rate only means something with a defined scope. Confirm the material, preparation, base, removal, disposal, drainage details and access assumptions. List work outside the rate separately, so a bigger area doesn't hide unrelated costs.
Can you measure a deck from a concept image?
A concept image shows a design direction, but it can't confirm square footage, slopes or drainage. Leave the quantity open until it's measured. You can give an item a zero rate on purpose, but you still need to confirm its quantity.