On the dive boats in NJ, there are lots of women divers. I'm sure sometimes there must be some instances of sexism, but for the most part I've seen very capable women divers "holding their own," and male divers treating them with respect and as equals. I do notice a little less trash talk when there are ladies on-board.
I've seen women ask for and give help to other divers just as much as most of the men divers, of course each according to their own level of ability and skill. If I'm walking empty-handed from the parking lot to the boat and I see another diver unloading their car, I will grab some of their gear, regardless if they're a woman or man.
About the only way that I'm aware I treat women differently is getting changed on the boats. None of the boats I dive on have changing rooms, so I will attempt to put on my dry suit underwear out of their view. I'm not shy and I don't care if they see "my stuff," and believe me, it's nothing worth looking at anyway, but I wouldn't want to embarrass them. I don't consider that sexist, I just consider it respectful.
Interestingly enough, I'd say half of the "mates" on the local boats I dive on are women. And they're a lot more qualified than me.