IT may be too late in the season to use traps but a minnow trap or crayfish trap thrown in now, or in early spring at ice out might be an important step.
First, many found out that the pond that was supposedly devoid of fish, somehow got stocked. Whether it was the eagle that flew over, the heron that swallowed the spawning fish and pooped out the eggs before taking off, or the helpful neighbors who saw water and thought it might be good to add something to it, or some other way, all your plans change in a mighty big fashion when you find out that there is something in your pond already.
IF the only thing you catch is crayfish, fine. If next spring you also catch other fish then we can identify them and start over from there.
In the meantime you can probably plan for sources of forage fish and start with them at ice out. Plan for building structure (research structure that is more snagproof since you want to swim and fish in it)
Also there is a little friction between those who want a crystal clear swimming pond vs those who want a 'fertile' pond full of microscopic critters, occasionaly helpful blooms, visibility of only 20" or so to prevent unwanted weeds, etc. There probably is a happy medium but the food chain doesn't thrive as well in crystal clear water.
Knowing what kind of crayfish are in your pond would be helpful too.
