Cut a length of nylon cord. Wrap one end around a shard of sea glass or pottery and double-knot to secure. Continue adding shards until you've completed a string for the bottom tier.
Apply a dot of cement glue between each shard and its knot.
Repeat steps 1 and 2 to make another string for the bottom tier.
Attach strings to a piece of driftwood with double knots, and apply glue between knots and wood. Tie a piece of cord loosely to the center of the driftwood; dangle mobile from cord, and adjust cord for balance.
Create strings for subsequent tiers, and attach to pieces of driftwood, working from the bottom up; check balance at each level.
Tie a length of cord to top piece of driftwood to hang.
Sea glass or pottery
Sea-glass pieces and ceramic shards, another beach find, can be combined in a Calder-esque mobile, producing a charming effect when hung by a window.
This mobile can be customized to include as many tiers or found objects as you like.