The dangerous part is becoming stranded by the incoming tide. You then have to wait six hours for the sea to go back out. There is no shelter from the elements and the island is so isolated that rescue could be difficult. Get local advice or better still go with someone who has local knowledge. The walk itself is easy enough on sandy beaches, in dunes and across mud flats. In wet weather and after spring tides, it can be very muddy. In the summer, there is a useful ferry that shuttles back and forth on the high tides for two to four hours per day. It's nice to walk about in the mud on a warm dark summer night because bioluminescent creatures light up your foot prints.