Chuck, I'm sorry to say that the rope may be your only choice. What I think you're thinking of would be like a 'baby gate' for use on stairwells, doorframes, etc. but would have to cover ~17' (if you have a Grecian pool, the width is probably 16' 6") and be at least 3' high (a little higher than the gates I have in my house) - also it would have to be constructed of materials which wouldn't be harmed by the pool water (ie, any metal parts would have to be SS - & good grade ).

I just had a small brainstorm - it might (!) be possible to make your own with the plastic mesh construction fencing (it should be the diamond style to prevent entrapment, though toes, fingers, hair may still be at risk even with the diamond style) secured to the wall with suction cups (or bathroom plungers) - I could see 3 cups per side attached to 1" pvc pipe to which the fencing is attached(on the sides)
Other possibility is using a safety rope to which said fencing is threaded onto (interspaced with the floats) and wighted on the bottom.
(I realse that there are some flaws with both methods, but the idea is only .5 hrs old - and I'm not an engineer ) *

Back to the safety rope - the, now defunct, NSPI required safety ropes to be installed 1' back from the change in grade (presumably to prevent nonswimmers from being able to accidently 'slide' under them) .


* (I know there are a lot of smart, knowledgable and ingenious folks here, let's all get together - design this thing and make some $ while increasing pool safety!! - needless to say the poolforum would get a cut off of the profits - maybe we can we can earn enough to keep it going forever!!