I don't know much about portal tombs but to me this is a beauty and very photogenic. As I say below just be careful with the tide, you won't get trapped or anything but it could be very uncomfortable.

Update:
Well I made it over to it yesterday at about 3pm (4th April) and the tide was well out. Im from the midlands so don't know much about tides you will have to check them yourself.
Its a great looking portal tomb, about 1.75-2m high and to me looks in great condition considering this gets covered in water everyday day of the year. It is actually facing east with, a large stone lieing flat covered in sea-weed that may be the missing stone.
The top of the cap seems to be white and I dont know whether this is the colour of the stone or some kind of paint on it.
To get there follow the path shown on the OS map, you pass some council houses one has a caravan parked outside, until you come to a fallen tree on the path. After this turn right and you come out of the woods into the beginning of the estaury/ wetland. Then just follow the edge of the water, I would advise bringing wellies and a good stick to check the mud that you are walking on.