lobster season ends feb 14th.
the coop (fish market) is open during regular business hours,, usually. there is also a fish store on the sidewalk called c-food.
beer delivery is do-able. i believe there is a 2 crate minimum. talk to Wallens (ace hardware)
you can rent a car and do several 'off the track' trips. a few waterfalls nearby, and just exploring is fun to me.
i wouldn't recommend any snorkeling off placencia itself. further north at false caye is very good but not from placencia.