We netted our pond at our previous house and had to disentangle grass snakes several times. They curl through the netting then play dead and froth as you snip away the plastic. Oscar winning performances because they all slithered off happily after I cut the last hold of netting. We often found the floppy egg cases in our compost heap.
I live on East Dorset/west Hampshire border and have seen three adders over the last two years on dog walks. Now those we keep a respectful distance from!