Calshot Marshes is an SSSI, Site of Special Scientific Interest in the New Forest. If you visit here you might be a bit 'errrr, are you sure about that?' at first glance, especially with the imposing and ever-so-grey closed down Power Station next to it, but really it is.
The geese you can often seen hanging out, you can get pretty close before they fly off and that's a real spectacle so if you go close and have a camera on you do get it ready to shoot. Not the picture postcard idyllic English country walk I know, but there's something pretty cool about the Power Station and the wildlife around it living in harmony so well. I find the Power Station building pretty cool to look at, now closed down, it never used to run very often, only at peak times and has always looked form the outside pretty desolate. It's somewhere I would love to get inside to photograph, and you never know that may happen in 2016 as they are planning to knock down the tower. It's quite the striking location with Tom Cruise filming part of Mission Impossible 5 there and the Millennium Falcon style building you can see three photos up appeared on Doctor Who many moons ago.
At present (December 2015) it's very boggy indeed and impassable without decent wellington boots.
You can park at Calshot Beach where Pay & Display parking applies (a menial amount of 80p an hour and £1.50 for two hours) or you can park for free at the car park by the Jolly Sailor pub in Fawley and walk along from there, a longer but enjoyable walk.