F1SHN:
did I mention I'm looking for info on Marco island diving.....?
DUH!
Way to be polite and make friends.
Walter did give you three great sites off Marco, and also gave you great advice about heading to the east coast to dive if you are not that experienced. The Gulf is advanced diving as the vis, water temp, and depths are challenging. I was about thirty miles off Naples on Sunday. The vis was about ten feet and the water temp about 60 degrees. That is a normal day in the Gulf.
The sites to dive off Marco are at least 1 1/2 hours out, and the better sites much further. There are almost no "dive boats" on the West Coast, but some fishing charters will take out divers- usually spearfishing trips. These trips are expensive due to fuel and time. Most run three tank trips/six packs for around $120-$150 per person if you fill the boat and do not include tanks. You will leave around 7 AM get in between 3 and 5 PM. Obviously, your charter will need to be set up way in advance. Also note, it is winter, so the seas can be VERY unpredictable and many trips are blown out. Many people do not like a 2.5 hour boat ride to 120 fsw a total of 45 minutes of bottom time, and another 2.5 hour trip back to the docks.
That is why Walter offered advice about heading to the east Coast or the Keys. There is nothing convenient or close in proximity about diving in the Gulf of Mexico. The days are long, the boat rides often miserable, the water frigid this time of year, the vis is usually poor, it is expensive, and pretty colors are rare. However, the spearfishing is very, very good. And if you want to see giant animals that get you heart racing then the Gulf is worth the hassles.