depend's which way you come into blyth m8, look for sign's for port of blyth, turn in where the huge yellow corragated shed's are, there's a small carpark. there's a hole in the wall which take's you onto blyth beach, there's a pipe there, either side of that really, but if it's a big tide you'll get pushed back.
you could walk through the security gate's and a swift 10 or 15 minute walk will bring you to blyth pier.
good luck.