Are you sure it needs to be air tight? It only needs to be air tight above the water level. So if one hose can be in the pool and up over the wall and then down near the ground, the other could be used to direct the flow where you want ... depends on how long your hoses are.
The contraption I use to connect the two hoses works fine for vacuuming, but, the connection is in the water when I'm vacuuming.
But, when I siphon, the connection, by sheer necessity, must be on the pool deck, hence, in the open air.
Each of the two 1.5-inch diameter vacuum lines works fine as a siphone all by itself:
But, now that I'm on the deep part of the pool, the hose has to climb ten feet out, and then snake another twenty or so feet flat, and then slope down another thirty or so feet, so I have to combine the two hoses to get 100 feet.
Every time I try to siphon with the two vacuum hoses connected, it sucks air instead.
Right now, I'm using a 100 foot long 3/4" diameter garden hose:
But, the flow out of the garden hose is downright puny, compared to the vacuum hose:
Plus, it gets all clogged with scum much easier than did the vacuum hose:
If I can get the vacuum hoses to connect without leaking air, the siphoning will take out most of the scum with the water:
So, the key problem now is how to connect two 1.5" diameter vacuum hoses to make an airtight coupling, so I can get back to the fast unclogged siphoning!