Actual size WAS about 18" long. Big enough that I dang sure wasn't going to test it and stick a finger in front of it! BUT - that sucker is now GONE. Where it went or how is a mystery to me. I checked on it all day the day I shot it and it hadn't moved. Next morning - it had disappeared. Sorry - if you wish you can just mark this report up to fiction or whatever. Heck, maybe I was just dreaming? That happens at age 77.
On the turtle traps, I bought one that was guaranteed to catch loads of turtles. Paid $80 for it on eBay

I tried it out for a week, but it never caught one single turtle. After the first week, it sunk to the bottom of the pond,


which is 15' deep. Never found it again, but the seller refunded my $80. He didn't, of course have to do that, but I didn't refuse the refund either.
Unless I get some workable suggestions on a good turtle trap, I'm going to lay a log from the water edge up the bank, for convenient turtle sun bathing, and use Eddie Walker's suggestion - i.e. target practice. This year we're overrun by turtles! Gotta do something...