There are boats that can taxi you to the arch. Pick them up in the Marina or on the beach.
If you want to go on a great fishing trip with a local, then go with Captain Almanza. He owns the 29' La Patrona. Last time we went out he charged $400 for a half day, plus a tip. We caught an 8.5 foot marlin, but he will fish for whatever you would like. He does half and full day trips. He has fished these waters for over 35 years. He said to call him in advance for August because his slots fill up. We had everything frozen and brought it back on the plane with us.
For the absolute best massages at the cheapest rate ($36 per hour), book at https://www.thesandbar.mx/. These massages take place on the rooftop of a bar overlooking the ocean. There may be other people getting massages, but you won't even know they are there. Once you are done, go downstairs and sit on the deck and watch the activity of Medano Beach. We highly recommend the Octopus appetizer. It is wonderful.