OK this wasn't such a sure thing as I thought. Stole hula hoop from pool shed and cut it into 2 36" sections. Happened to have 1/2" CPVC pipe in basement and it was the same diameter as the hoop so the fittings worked. Happened to have some black nylon screen in basement and squared off the ends. Sewed a 1 1/2" deep hem in each of the long ends. 
Drove to Ace hardware because I only had one elbow (OW). Bought some fittings. Put it together. 
Was not happy with the way the screen sagged in the middle. Decided it needed support in the center. Had only 1 T. Drove to Ace hardware and bought a bunch more fittings including more Ts and another 10' length of CPVC. Took version 1 apart and made a slit in the center of the hem and pried it open to insert a T in the center of both ends. Cut the original hoop 36" pieces in half, making 4 18" pieces. Shoved the hula hoop pieces into the Ts inside the hem. Put an elbow on the 4 exposed hoop ends and shoved a piece of pipe into the open end of the elbows and into the open end of the Ts at the top. Picked it up and it was too wobbly. Took the version 2 apart or was it 3. Removed elbows and cut 4 1" pieces of pipe. Put Ts where the elbows were because I decided it needed cross pieces laying on the bottom of the pond. Used the 1" pieces to attach the elbow to the T and then put in the cross pipes. HMMM, not bad. OK the hoop pieces aren't really thrilled to stay in the top Ts but seeing they are inside the hem, they stay put at least. 
I didn't glue anything either. Could have but decided that I might want to take it apart to store or tweak it some more. Hauled it upstairs and tossed it in the pond. Watched it float nicely. HMMMM, should have drilled holes in the high areas. One of the hoops came apart from the top Ts and so let the air out and eventually it sunk. PHEW!! 
Fish are scared to death of it of course.
Drove to Ace hardware because I only had one elbow (OW). Bought some fittings. Put it together. Was not happy with the way the screen sagged in the middle. Decided it needed support in the center. Had only 1 T. Drove to Ace hardware and bought a bunch more fittings including more Ts and another 10' length of CPVC. Took version 1 apart and made a slit in the center of the hem and pried it open to insert a T in the center of both ends. Cut the original hoop 36" pieces in half, making 4 18" pieces. Shoved the hula hoop pieces into the Ts inside the hem. Put an elbow on the 4 exposed hoop ends and shoved a piece of pipe into the open end of the elbows and into the open end of the Ts at the top. Picked it up and it was too wobbly. Took the version 2 apart or was it 3. Removed elbows and cut 4 1" pieces of pipe. Put Ts where the elbows were because I decided it needed cross pieces laying on the bottom of the pond. Used the 1" pieces to attach the elbow to the T and then put in the cross pipes. HMMM, not bad. OK the hoop pieces aren't really thrilled to stay in the top Ts but seeing they are inside the hem, they stay put at least. I didn't glue anything either. Could have but decided that I might want to take it apart to store or tweak it some more. Hauled it upstairs and tossed it in the pond. Watched it float nicely. HMMMM, should have drilled holes in the high areas. One of the hoops came apart from the top Ts and so let the air out and eventually it sunk. PHEW!! Fish are scared to death of it of course.