That E-Z Patch looks great. I wonder how well it bonds and if anyone here has used it for any length of time. It appears that it can only be used for defects 3/8" or deeper. That sounds like it should work in this case. Just make sure that the edges aren't loose; chip away until you get tight plaster.
A few years ago I patched a few small defects in my pool with Epoxybond Pool Putty. The repairs were done underwater and have held-up well. The advantage of the putty is that it can be applied in a rather thin coat, I even wiped it on a couple of just worn areas and it took OK. The downsides is that it's not easily troweled, the texture is very different and the white was much whiter than my old plaster so my patches are obvious. The most difficult part of my application was trying to work in my deep end without scuba gear. I used a weighted bucket to hold me down by one hand and only had one hand to apply and smooth the putty, this with one held breath. I'm not sure I'd try that approach again.
