Can I just buy this stuff in Mexico?

Yes, but it will be marked up significantly in tourist zones. You will pay 2-3 times more for name-brand sunscreen at a beachside shop than you would at home.

Do I need water shoes?

If you are visiting cenotes or rocky beaches like those in parts of the Riviera Maya, yes. The rocks can be sharp and slippery.

Essential Beach Gear for a Mexico Trip

Pack high-SPF reef-safe sunscreen, a lightweight sand-proof beach blanket, and a dry bag for boat excursions. You need gear that handles high humidity and intense UV exposure without taking up your entire carry-on allowance.

Select the right sun protection. Mexico’s sun is stronger than you think. Bring at least two bottles of 50+ SPF sunscreen. If you plan on snorkeling in cenotes or reefs, ensure it is 'reef-safe' (zinc or titanium-based) as many protected sites forbid chemical sunscreens.
Prioritize a dry bag. Bring a 10L or 20L roll-top dry bag. It keeps your phone, passport, and wallet safe from sand, salt spray, and water during boat transfers or beach days when you don't have a locker.
Pack a sand-free towel. Don't bring a bulky cotton towel. Bring a microfiber travel towel or a 'sand-free' sand-repellent beach blanket. These fold down to the size of a paperback book and dry in under 30 minutes in the humidity.
Prepare for the bugs. If you are heading to the coast, sand flies and mosquitoes are common at dusk. Pack a DEET-based repellent or a natural alternative with lemon eucalyptus oil.

Can I just buy this stuff in Mexico?: Yes, but it will be marked up significantly in tourist zones. You will pay 2-3 times more for name-brand sunscreen at a beachside shop than you would at home.
Do I need water shoes?: If you are visiting cenotes or rocky beaches like those in parts of the Riviera Maya, yes. The rocks can be sharp and slippery.