Having cleaned many a mud pit in my time, the best way is usually the simplest and messiest. Buckets and a shovel should do the job. If there is water in the pond, you can try a submersible pump, but this will most likely be more of a hassle that it is worth being that it will clog very regularly given the type of debris the pond has collected.

Once all the debris is removed, the concrete can be cleaned with a power washer in conjunction with a shallow sump pump (to remove the water you are spraying into the pond).

Inspect the concrete once it is clean. Repair any cracks or potholes with a smooth mortar mix. This would also be the time to re-waterproof the concrete by painting it with a product such as Thoroseal.

Thanks for your advice, do you have any suggestions for scarying off any snakes that might be in the pond. Eepps

Thanks for your advice, do you have any suggestions for scarying off any snakes that might be in the pond. Eepps