When i got certified back in '88 Sudafed was recomended by my instructor before every dive... Now it's a No-No..
I dive alone sometimes, but only on shallow beach dives, or when working on the boat tied up at the marina...
I once left a boat un attended... I'll NEVER break that one again... cause we also underestimated the current, and almost got washed clear out of Vineyard Sound.. i am VERY grateful the anchor held in all that current... And that a passing boat was able to pluck my buddies and i out of the water and shuttle us back to the boat.
I've been diving for a while now.. and although i've added Nitrox and Drysuit certifications, i still have not gotten my Advanced Open Water, but often dive deeper and enter wrecks, but never alone...