I'm quite lucky, I actually work a short walk from Britain's coastline. Which means that at lunchtime on a nice day I can go for a walk on the beach. The downside is that while it is technically part of the coast, the river Thames doesn't have a beach for much of the day. For the geographically challenged, the Thames is the river that runs through London England, past Big Ben and under London Bridge.
Not a lot of people realise this, but the Thames actually has a rather fine sandy beach on the south bank and most days, at low tide you can find people making sand sculptures in the hope that the tourists will chuck money at them. There are many places on both banks where you can access the beach, though you may well have to climb over a small wall or gate to access the steps. On the whole the beach is littered with all sorts of things that have washed up with the tide some of which are hundreds of years old. Only the other day I found a rather fine clay pipe that had been discarded in the 17th century. Quite often you'll find bones, in fact there is a small bay on the north bank that has a beach that consists entirely of bones and oyster shells that were dumped in the river by the stew houses in the area for hundreds of years. You can also find more modern flotsam and jetsam, that could make an interesting photo. You can pick up anything you find on the surface, but you will need licence if you want to start digging.
Of course getting down on the beach gives you a different perspective on the area, because you can get closer to the water than normal and, if you're not careful, in it. You'll need stout shoes and be aware that in some places the sand may be softer and dirtier than others. You should also make sure you know what the tides doing and don't get stuck anywhere that you can't get out of. In some places the beach is only a foot wide so you don't want to walk too far along where when the tide is on the turn, because the only other way out is up some very steep walls.
If you live in London, or are visiting, you can get a weekly prediction of the tides from The Admiralty Easytide Prediction Service. Its sometimes useful to also know when the high tides are going to be for those times when a low tide would ruin your shot.
So if you live in a classy city like London, on a tidal estuary, go get yourself some tide charts and some wellies and take a walk on the beach.