I have seen the seal in Brighton Marina a couple of times. Firstly in the outer harbour where it was happily catching and eating fish. However, I was a bit surprised to find him so close to my boat when preparing for a trip.
The photo above was taken by my boat in the harbour. The seal swam up to about a metre from me. He is very inquisitive and after seeing what was going on continued to swim about very close to the boat.