Plan the position before you lift a spade

A small pond is one of the finest things you can add to a garden. It brings frogs, newts, damselflies and drinking birds, and it gives children a window into a world that moves at a slower pace. It also needs thinking through, because water and small children are a combination that deserves respect rather than fear.

Position matters more than size. Put the pond where you can see it from a kitchen window or a favourite chair, and never in a corner hidden by a shed, behind a hedge, or at the bottom of a slope where runoff collects and nobody looks. Keep it away from the route between the back door and the trampoline, and away from swings and sandpits, so that a running child is not heading straight for it.

If you childmind, or let the garden as a holiday property, check what your registration or insurer expects before you dig. A sunken pond is the usual choice, but a raised one with walls 60cm or higher is worth considering while children are tiny, because the water sits further from small hands. It is not a substitute for supervision, and a determined four-year-old will climb anything, so plan for both.

Build in gentle slopes and a wide shallow shelf

The shape of the pond matters as much as the fence around it. Aim for sides that slope at roughly one in three, so nobody who ends up in the water is met by a vertical wall. A preformed liner with moulded shelves and gently swept sides is the simplest way to get this right; if you are using a flexible liner, mould the slope carefully and pad it well with underlay.

Around most of the edge, create a marginal shelf 20–30cm deep and at least 30cm wide. Along one side, shallow it further into a pebbly "beach" that a child can walk into and out of easily — 5cm at the rim, deepening slowly. Keep the deepest point in the middle, and no more than 60cm in a small garden pond. Wildlife needs depth for overwintering frogs and newts, but a modest deep zone is plenty.

Fill the pond with rainwater where you can. Tap water across most of the UK contains chlorine or chloramine, which will not do your plants or your pond creatures any favours.

Choose edging that stays put

Loose cobbles and gravel margins look lovely and shift underfoot, so the edge of a pond is exactly where they should not be. Set paving slabs or clay bricks on a firm mortar bed instead, with a small overhang to hide the liner and a flat, stable surface underfoot. Avoid slippery timber decking at the water's edge, or choose a grooved, anti-slip board if you must use it.

A low barrier is not a sign of failure — it buys you time. A 60–70cm willow hurdle, chestnut paling or simple picket fence around the water, with a self-closing latch on any gate, keeps toddlers out while still letting you sit and watch the dragonflies.

Hide the water storage and working parts

Pumps, filters and top-up reservoirs are best buried out of sight and out of reach. A sump or reservoir under a pebble-mulched area or a small deck can hold topped-up rainwater, fed by a pipe from a water butt, so you are not carrying cans across the lawn. House any pump in a chamber with a bolt-down lid, and protect outdoor sockets with a residual current device.

Then walk the garden once a week and empty anything else that holds water:

• buckets, trugs and wheelbarrows
• paddling pools and their covers
• plant saucers and old sinks
• half-full watering cans and pet bowls left outside

A toddler can drown in 5cm of water, and the pond is rarely the biggest risk in a family garden.

Fit a hidden safety grid if a fence will not suit

Where a fence would ruin the view or the budget, a rigid grid set just below the surface is a neat compromise. Use strong plastic or metal mesh with openings no larger than about 40mm, laid 50–75mm below the waterline on a frame or pegs so that it spans the whole pond and takes a child's weight without sagging. Frogs, newts and insects pass through the gaps; a child's foot does not. Let blanketweed and floating plants soften it, and check the fixings every spring and after winter storms.

For a tiny wildlife pond, a removable rigid cover that clips into place can be lifted for maintenance and put back in seconds. Neither option replaces supervision — they simply give you a few extra seconds if your attention slips.

Plant the margins, teach the rules, keep watch

Marginal planting — water mint, marsh marigold, lesser spearwort, ragged robin — softens the edge, hides the grid and gives emerging frogs somewhere to climb. Keep the grass or gravel immediately around the pond short and level, and avoid plants that make the approach slippery when wet.

Rules work better than warnings. From the first summer, teach children to sit down to watch, never to lean over the edge, and to fetch an adult rather than reach for a toy that has blown into the water. Say it often, and say it plainly, and let them help with pond dipping in a shallow tray well away from the edge.

Above all, never leave an under-five alone near water, not even for the minute it takes to answer the door. Set the pond up so that a few seconds of inattention are survivable, then make sure those seconds never have to be tested.