So much good advice here (and elsewhere!) so far.
So it looks like we won't be doing the Dolphin Experience and Turtle Farm in Grand Cayman based on reviews. We'll be saving that for Discovery Cove the following week when we come home from the honeymoon. Which means we'll have a free day at Grand Cayman to hang out at Seven Mile Beach, explore the ship a bit, or do some browsing around the touristy areas of town.
I think we're still going to do some Excursion for the ruins when we get to Costa Maya...unless any of you recommend a way to just do this on our own for less than booking an excursion for it. I really don't care which Mayan Ruins we go to...just feel like we should see atleast one!
In Cozumel I think we'll be going to Xplor Park...I know it's bloody expensive, but it looks like a real hoot between the 13 Zip Lines, riding amphibious vehicles, rafting in an underground river, etc... I think we might be taking a chance with this one!
I don't know if we're going to book anything for Castaway Cay except maybe a massage (if I can get over my weirdness factor of it). Yoda recommended that we bring our own snorkeling equipment as the stuff at the Cay is pretty cheap, so we're going to look into doing that!
May 12th is going to be here before we know it!
Since it looks like you will be going the own equipment route I'll post my suggestions here so that others looking do do the same will have a head start. I am by no means a pro caliber diver but the advice I got was from several people who are and it has served me well.
Snorkeling equipment is at its heart incredibly simple. You need a mask to see through, a tube to breath through and fins to swim with. As long as you have met those three criteria, you will be fine. However, inside of those things you will you will find many options, some necessary and some suggested.
1. Mask: A good, well fitting, and comfortable mask is essential. Silicone seems to be the current material of choice and you will find that even inexpensive masks are made of it. To see if a mask fits hold the mask up to your face, do not put the strap over your head, and inhale gently through your nose. The mask should stick to your face and you should not have any air leaks. If it falls off your face or leaks, select another mask. A few options you will want to have on a mask are....
A:A one way purge valve. This will let you expel any water that gets into the mask by exhaling through your nose.
B:Thermal lenses. These are not essential and can be pricey but they will not fog as easily as a standard lens.
C: Panoramic Lens: This is a lens configuration that wraps around the side. Again this is not essential but is does improve your peripheral vision.
D: Neoprene strap or strap cover: Again not essential, but they will make the mask more comfortable to wear.
2. Fins. Fins come in a myriad of shapes, sizes and configurations. I have no idea how much the weird shapes actually help but there are a few things you will want to look at when selecting a pair. The way they fit on your feet will be one of the most important factors. Fins either attach via a full foot or a strap on the back.
Full foot
Strap
Both have their pros and cons. The full foot design will protect the bottom of your foot much like a shoe but the are a pain to get on and off and fit can be a bit inconsistent. Strap fins are easier to get on and off and they tend to fit better. Many people I know will get neoprene booties to go along with these fins to protect the bottom of their feet.
For occasional snorkeling I would avoid a super stiff fin. A stiff fin will transfer more of your energy into the water but it can feel like having boat oars tied to your feet and an be quite fatiguing.
If you plan on flying with your dive gear in the future look for a travel fin. These are a bit shorter and will sit into most carry on luggage.
3: Snorkel: These are pretty simple. You want a dry (not semi-dry) snorkel with a one way purge valve on the bottom. These snorkels close off when you submerge so you do not get a mouth full of sea water every time you dive down.