Many DSMB's have an attachement point for a slate or wetnotes.
Good idea and very observant.
http://www.omsdive.com/lift-smb.html
In the UK, DSMB's with their own little scuba tanks are the norm I believe. Here in the US I am starting to to see ones with little CO2 cartridges. They are being used by hunters here to send up their catches. Not as personal markers.