Tips for going to Green Island

I hope this is not too redundant, but I have read the old Green Island thread and didn’t find all the information I’m looking for. I’m planning a trip to Green Island this weekend.

Can I really just go to the harbour in Taidong and buy a ticket to Green Island? Do boats leave frequently?

The main reason I want to go is to snorkel. Are the conditions always pretty good? Do I have to go at a certain time of day?

Any input on good or bad experiences would be appreciated!