The water can get quite rough on windy days so just take care. You may also spot the occasion seal swimming in the water too. The tide goes out very far -- avoid the temptation to pitch on the shore for swim when it is out as you'll get marooned when it comes back in either side of you.
The water quality is amazing so no need to worries about sewage here. SEPA monitor the water just up the coast at Seacliff if you want to check the data: https://www2.sepa.org.uk/BathingWaters/ViewResults.aspx?id=4403
Edinburgh Skinny Dipping Stories facebook group: https://www.facebook.com/groups/skinnyswimmers