Now that we are flying from PHL to places in the Caribbean and this is new to us I thought this would come in handy. A captain I flew with showed me this video. Explains about SLOP procedure in the WATRS (and other) routes. Different than other deviations. I know you can only get some much from the manuals.

https://youtu.be/HBF31B5W_R8

if you guys that have experience flying transatlantic have any other tips feel free to chime in.