This post is all about warning DIYers against the idea of fitting an electrical supply in your garden for a pond or water feature.
Any electrical work carried out in the garden should be done by a suitably qualified electrician. Check out this site to find one in your area.
The installation of cables and electrical equipment in a garden has to be done correctly and to current regulations, it is not a job that a DIY enthusiast should attempt.
All electrical circuits in a garden have to be protected by a suitably sized fuse/miniature circuit breaker and an RCD device.
Any cable supplying a pond pump or water feature and any other electrical equipment must be suitable for outdoor use. Ideally small wire armoured (SWA) cable should be used for an electrical supply from your property out to the garden pond pump or water feature. It should be buried in the ground at a depth of 20 inches (500mm).
The cable should be bedded in sand and then covered with approximately 6 inches (150mm) of soil, then a ‘Live cable below’ warning tape should be ran the length of the cable trench. The trench can then be completely filled to the ground level.
The 6 inch (150mm) difference in depth between the warning tape and cable allows anyone who is excavating soil in the vicinity of the cable to dig up the warning tape first, hopefully without damaging the cable at the same time.
You can run cables outside through conduits, but I think if there were any savings to make they would be negligible against the cost of SWA cable.
I would get advice from an electrician and see what they recommend. You can always save money by excavating the cable trench yourself rather than paying the electrician to do it (I am confident the electrician would appreciate it being done by others).
There are outdoor/garden electrical kits available which might suit your requirements but again, check with your electrician.
As I always suggest, try and use an electrician recommended by friends or family members.