I've removed the three crew members. Their accounts are still active and it looks like two of them are following your boat still. It's best only to add crew members for permanent people on the boat.
There's no point deleting the accounts used with the email addresses you mentioned as an accidental log in with them will just recreate the data. They're not associated with your boat in any way so will lay dormant. If you get emails to these accounts that you don't want, then use the link at the end of the email to change the preferences for those addresses and turn them off.
I hope that helps.