A suggestion for local divers on who to call, depending on the location:
Calling 9-1-1 from that beach would have activated either Island or Skagit County EMS. I suspect their response time would be pretty good. On the other hand, if you're diving San Juan County and not near Friday Harbor (e.g., in Rosario Strait), might be better to call Coast Guard dispatch. San Juan County response won't be as fast as Coast Guard. (I lost a friend who survived a small plane crash in Rosario Strait, but died of hypothermia before SJC EMS could get to him. Coast Guard likely would have saved his life because they would have been on-site substantially faster. Like 20-30 minutes, not an hour and a half.)
Personally, if boats were needed for a rescue situation, I'd try to call both 9-1-1 and Coast Guard. In my DM training, my emergency plan was for a remote location like this and I talked to USCG about what number to call. (They were happy to hear I was being proactive.)