This isn't necessarily a bad thing though, as it increases the array of choice for any Northamptonshire based, would-be beach go-er, opening up beach opportunities on both the West and East Coasts of the UK (and some, perhaps surprising beaches, locally).
Technically, the nearest beach based on the sea, is Snettisham Beach, in Norfolk, offering miles of sandy coastline, local wildlife, and bird watching opportunities, however this does require a 66 mile drive.
However, if the presence of the sea isn't paramount, the nearest beach to Northampton is at Bosworth Water park (based around a lake) a mere 31 miles away, offering 20 acres of watersports, paddling pools, and a man made beach of golden sand. Unlike Snettisham, because Bosworth Water Park is purpose built, it is packed full of all manner of amenities and enticements to entertain everyone, young and old.
From Canoe hire to Barbecues, windsurfing to pirate adventure playgrounds, it really is impossible to get bored here. Likewise, Keynes Country Park, situated in the idyllic Costwolds, offers a lifeguard supervised, sandy beach around a lake, once more, offering great amenities like Barbecues, play areas & country walks in the tranquil settings of the park. At 56 miles away from Northampton, this is a bit of a drive, but it does receive glowing reviews and is Northampton's second closest beach.
So, even though Northampton is smack bang in the centre of the country, it doesn't mean that you need to drive all the way to the coast to have access to a great stretch of beach.