How about a long-handled net like they use for scooping up fish or for cleaning pools?

And, if you happen to snag it and lose it again, have a float (say, a weight, a 10-ft piece of string, and a fishing bobber or piece of styrofoam) to mark the spot. You can toss it right in where you think that the engine is.

My guess is that the engine broke off when it hit the water's surface and is perhaps a couple of feet away from where you picked up the plane.

Just my $.02

Bob