Been here diving for a month. It was a little wavy (nothing serious) in late September, but since October, the surf and seas have been essentially flat. (A day or two of mini surf, ⅓ meter, at the past new moon.) The currents have been negligible as well and the vis has been fantastic. As previously mentioned, depending on your age/fitness level, entries/exits can be tricky if there is any surf in Tulamben, due to the presence of pebbles and boulders making it difficult to get a stable footing. As mentioned, if you have them, definitely bring rigid-sole booties (not soft ones). These make it much easier. You dive guide will also assist with entries/exits if necessary.
If there is any surf, or if you just want extra safety, enter AND exit with your reg in and mask on. Then if you get rolled, at least you can see and breath. If you do get rolled, DON'T try to stand up (you'll just get knocked down again), get on all fours and either crawl back to shore and try again, or better inflate a bit (should be done before entry) crawl into the water and float up to the surface, and then don fins and swim out.