Google the images for hollyhock. Foliage is fairly dense at the bottom of the plant to support the tall growing flower stalk. You can plant them close together (or they'll seed themselves that way eventually), but they definitely won't screen the pool from people walking by on the other side of the fence.

You might look into small footprint but tall growing conifers - some of the Thuja varieties - for real screening. But a 24" wide bed does limit your choices.

Someone is bound to suggest growing vines on the fence or adding a trellis to the fence and then growing vines on it.

I've pretty much given up on hollyhocks since they get rust (disease) badly and end up looking awful.

You could check out Jerusalem artichokes, which are a type of perennial sunflower (with edible root tubers) that weren't affected by any pests or critters when I grew them and will fill any space you give them. A 24" wide bed of them should provide a good screen.

As Duluth suggested, vines are a good idea for a narrow screen. I've grown scarlet runner beans for a screen. They're an annual that I just grew up strings. One of the more robust clematis or one of the native honeysuckles might work well, too. You'll need to choose the best type of support for the vine you choose, but since I don't know what type of fence you have, I won't make any suggestions. Beans and honeysuckle twine around supports with their stems and clematis with the leaf stem (petiole.)

Folks on the conifer forum will likely be able to give you ideas on some of the narrow conifers.

Is your pool close enough that you need to choose a plant without much litter?

I do like the idea of honeysuckle thanks. Personally, I am not a fan of conifers. No, the pool is a good 10' away. Maybe some honeysuckle and cosmos in front. BTW, just googled jerusalem artichoke and you id'd a plant in my flower garden for me! I like them but I am definitely overloaded with yellow in my yard. It is a pathway that is seldom used. Maybe two people a day pass by so I am fine with minimal privacy. I just don't want anything that turns ugly and sounds like hollyhocks would suite better at the back of the garden. Thanks.

I have hollyocks in my garden that get to be about 4' across at the base. This may not be a common thing, but just sayin'. Besides, they tend to get leaf miners and weevils that make them look lace-leaved in the summer. They are a biennial, also, not a perennial. I would put them at the back of a bed, also.

Rust is a terrible problem for me too, they only look good from a distance.