@cycleguy41
Sorry for bothering you. I forgot the topic poster is you and thank you for your answering and reminding me that.
I will ask @jaffadog through messege.

@cycleguy41 @jaffadog

I mean on the http://www.fastseas.com/. There are two lines in the map. One is a greatcircle, the other is a straight line owing to Mercator projection. Both two line show well in the wind mode, but when I switch to the waves mode or currents mode these two lines will be under the land. I have the same problem while using Windyty in my map and I have tried zIndex option in polyline in leaflet, but it doesn't work.
Thanks~

@jaffadog
hi! I wanna ask that is there anyway to let the polyline show on the land while switching to wave and current mode.
i've checked the leaflet doc, but it seems that there is no zIndex in polyline option.
Thanks~