Getting rid of water boatmen from your pond they if they are eating my goldfish.?

Any outdoor pond will gradually acquired wildlife including various insects, frogs, etc. They are a sign of a healthy ecosystem. If the pond has a wide, balanced, assortment of life it can become self-sustaining and you won't need to do much of anything for maintenance.

Depending on where the Asker is located:

In the US, Corixidae are called Water Boatmen and are not predatory insects, feeding mostly on green algae, which most people owning decorative ponds are happy to be rid of anyway.

In the UK, what are referred to as Water Boatmen or Back Swimmers are a slightly larger insect of the related family, Notonectidae. These insects are predatory and some species can even eat small fish or tadpoles. So if you are trying to introduce those to your pond, you might either grow them in an indoor tank until of sufficient size to not be eaten or else obtain a sufficient supply that the Boatmen can't eat them all.