I am very surprised about the sequence of the waves, it would have been way better to have the M50 and M25 in front of me, and the M65+ and W55+ behind me.
Me myself a BOP swimmer (1.25' in 2019), expect at least after the turning point the majority of M50 and M25 overtaking me. On the other hand, I expect to have to overtake a considerable amount of the M65+ and W55+.
I thus wonder about the swim etiquette.
Keep right, pass left? No idea.
Maybe someone of Ironman reads this here and works out some advice which can then be conveyed at the race briefing.