A simple but very effective solution where your pond has no marginal shelves and the pond is too deep for marginal planting.  Most marginal plants fall in the planting depth range from 0 - 20cm, so if your pond either has no shelves or steeply sloping sides these mats are the easy answer to your problem and avoid the effort and expense of creating shelves.  The black fabric mats measure 110cm by 105cm and have 3 rows of 6 pockets (it is not recommended to use all the pockets!) for holding soil to plant your marginals in at different depths.  They have holes along one edge and come with pegs for anchoring the mat in the soil around the pond edge.  Alternatively they could be held in place by stones if the pond has a concrete surround.  Planting creeping varieties in the top row is a good way of covering the edges of the pond and masking the fabric.