Will a female turtle without a male lay eggs? I have 2 red ear silders indoors and last night I swears one of the dug a pit into the sand island we have in their pond and was lying eggs. I though I took a picture of it but when I went to download it today it was not there so there must not have been enough light and I did not want to scare her by getting closer while she was straining tail down in the pit. Today the hole is all smoothed over and looks like normal. 
Yes, female turtles will lay with or without males. Females who have been exposed to males can store the sperm for up to five years and lay fertile eggs. Females who have never been around males will still produce the eggs and
must have access to dirt to lay them. Some who don't have access to dirt will drop the eggs in the water where the eggs (if viable) will drown. Yes, drown. Turtles lay permeable shelled eggs which must be allowed to breathe - and yes they can breath while buried in the dirt. (This breathing thing is why a lot of eggs seem to hatch just after a rainstorm in the summer.) Other turtles who do not have access to dirt to dig a hole and lay their eggs will just hold them inside - sometimes they are reabsorbed, but more often they bind and end up killing the mother turtle.
When turtles dig their hole and lay their eggs, they end up covering it in such a way that it looks like nothing was ever there. They even manage this when digging in the hard-as-a-rock georgia red clay - which is completely amazing.
