Fence the water properly, not hopefully
The single change that prevents pond accidents is a physical barrier your dog cannot push through, jump, or dig under: a sturdy fence or railing around the pond with a self-closing, self-latching gate, because gates left ajar by children and visitors are how most fenced ponds still fail. Low decorative edging and netting do not count as barriers, and netting carries its own risk, since a dog who steps onto it can become tangled at the water's edge. Walk the fence line from your dog's height and strength, checking for gaps at ground level, loose panels, and anything climbable stored beside it.
Build in a way out for the fall that still happens
Even with fencing, plan for the day a ball, a frog, or a visiting dog defeats your precautions. A pond with at least one gently sloping side, a submerged shelf, or a firmly fixed ramp lets a wet, heavy, panicking dog haul himself out, where sheer vertical liner walls can defeat even a strong swimmer. Keep the exit route unobstructed by pots and ornaments, and show your dog where it is during calm, supervised introductions to the fenced area, so the knowledge exists before he ever needs it in a fright.
Train the pond boundary as a house rule
Teach your dog that the gate line is a boundary he does not cross without you, using the same calm repetition you would use for a road edge: reward checking in with you at the gate, practise recalls away from the pond with high-value rewards, and never encourage chasing toys toward the water. Puppies, elderly dogs, heavy short-legged breeds, and dogs who cannot swim well need the strictest version of this rule and should never be in the pond area unsupervised, fence or not. Consistent rules from every person in the household are what turn training into a habit he keeps when you are not watching.
Manage the quieter pond hazards too
Ponds hold more than water risk. Stagnant edges can grow algae that is unsafe to drink, ice in cold weather invites a step onto a surface that will not hold his weight, and pond plants, treatments, and the fertilisers used around them should all be treated as things your dog must not eat or drink. Discourage drinking from the pond by keeping his own fresh water bowl nearby in the garden. If he does fall in, swallows a lot of pond water, or seems unwell or unusually tired afterwards, contact your vet the same day and describe what happened. Put the gate rule, the no-drinking rule, and the exit location into his profile in KinsLe through Family Sharing, so family, sitters, and visitors all enforce exactly the same pond safety plan.