Hello!
These spiders are always creating webs across my pool and spa.
Just wondering what they are.

Thanks!

Looks like a water strider
https://www.nwf.org/Educationa...

.. except for having the wrong number of legs, the water strider being an insect, not a spider
I'm not having luck yet with my google of 'florida spider long abdomen'. The closest picture that came up was from a pest control company and must have been a random 'spider' picture grabbed from the internet.

is it a traditional orb web? that could help the ID.

Haven't been able to see the web - It only comes out at night and the pool light makes it difficult to see the web.
I'll keep trying.

Are they living in/on the water, or are they on webs over the top?

Webs over the top of the water only - From one side of the corner tile/deck coping to the other.
They do catch a lot of flying insects in that area.

Looks like a long-jawed spiders (Tetragnathidae). Their feature are their large chelicerae / fangs (in some species can be longer than their cephalothorax), slim body with long legs
They prefer to live near water, frequently build web over ponds, streams, or bushes. Web often parallel to the ground/water bodies, and weak compared to most orb-web spiders.
They can walk on water almost like water strider (insect in Gerridae), using surface tension in case of need.
For comparison image from https://www.waynesword.net/Tet.... note the long chelicerae (fangs)

With Tofi.
These spiders are always in the pond water , pools , etc. They are on the surface of the water having legs that are like floaters. They always looks some what intimidating. I usually just take the net and fish them out.

Nice detective work, Tofi.

Thanks to all for helping.