Hi, my wife and I will be finishing up in Utila around April 19th and we fly out of Belize City April 26th is it possible to make it up to Caye Caulker for a few days of diving or is that unrealistic with the ferry schedule?
It depends on which you are more willing to spend, time or money. It's possible to get there a variety of ways - land and land/sea options - but the quickest would be to fly (possible at least some days).

Unless you are flying, it might be easier going to Placencia. There are two ferries going from Puerto Cortes(about a half day bus trip from La Ceiba) . One(The Express) goes on Monday mornings to Placencia, the other(Nesymein Neydy) goes to Dangriga on both Monday and Tuesday mornings.

Here are the water taxi schedules as at December 2008...
DANGRIGA, BELIZE TO PUERTO CORTES, HONDURAS
“Nesymein Neydy” departs from Dangriga on Saturdays. Passengers should be at the dock at 8:30 a.m. for immigration processing. The boat departs about 11:00 am.
Arrives at Puerto Cortes about 1:30 pm.
Return trip: Departs Puerto Cortes on Mondays at 9:00 a.m.
Cost: US$55.00 each way (plus any exit fees)
PLACENCIA, BELIZE TO PUERTO CORTES, HONDURAS
“D-Express” departs from Placencia on Fridays. Passengers should be at the dock at 8:30 a.m. There is a stop at Big Creek.
Arrives at Puerto Cortes, Honduras about 2:00 p.m.
Return trip: Departs Puerto Cortes, Honduras on Mondays at 9:00 a.m.
Arrive Placencia at 2 p.m.
BZ$110.00 each way (plus any exit fees).
Tickets available at the Placencia Tourism Center. Tel: 202-4506 or 523-4045. Email: placencia@btl.net
http://www.belizeferry.com/Welcome.html
a601mom,
Have the schedules changed since December? Are the water taxis running on Tuesdays?
One of the Belizean airlines has a flight between Honduras & Belize. I forget which one, but here are the links...
http://www.tropicair.com/
http://www.mayaislandair.com/
From Placencia to Caye Caulker, you can take a bus to Belize City then water taxi to CC, or fly. You have lots of time to do the trip.
Here's a short primer on travel between Honduras and Belize. Remember
that schedules and even routes do change.
While Belize and Honduras are geographically not far apart, the
problem for a long time has been that travel between the two countries
is difficult and time-consuming.
Belize-Honduras travel connections are improving, but they remain less
than ideal.
BY WEEKLY FERRY
There are two weekly boats between Belize and Puerto Cortes, Honduras:
D- Express leaves from Placencia on Friday morning (check in at 9
a.m.) and the Nesymein Neydy from Dangriga on Saturday morning (check
in at 8:30 a.m.) D-Express returns from Puerto Cortes Monday morning
and Nesymein Neydy on Tuesday morning. Cost is US$55 each way. To
confirm times, etc. for D-Express check with the BTIA office in
Placencia -- email BTIA@placencia.com or call 501-202-4506. For NN
try 501-522-0063 in Dangriga. You could also check with Mundo Maya
Travel in the Marine Terminal in Belize City, 501-223-0457 or email
mundomayatravels@yahoo.com, as they'll make reservations and sell you
a ticket.
There are other options.
BY WATER TAXI FROM PUNTA GORDA TO GUATEMALA
You can bus or fly to Punta Gorda and take one of the three daily
water taxis from Punta Gorda to Puerto Barrios, Guatemala (three
different outfits – Requena’s, Pichillingo and Marisol -- with
departures at 9:30, 2 and 4 respectively, around US$20--$22), and then
from there make your way by shuttle to the border and bus to San Pedro
Sula. This is your cheapest option. From Puerto Barrios, reverse the options.
There is also twice a week service between Livingston and PG.
FLY MAYA ISLAND AIR
Another option is to fly between Savannah (across the lagoon from
Placencia, with connections from other points) on Maya Island Air
nonstop and San Pedro Sula. Fare is US$163 -- not sure if Maya does
their cash discount on this flight or not. The web site suggests the
flight is daily, but it's not -- email or call Maya for the current
days they fly (www.mayaislandair.com ).
FLY ATLANTIC AIR
I believe, but haven't checked recently, that Atlantic Air is still
flying three times a week -- Monday, Wednesday and Friday -- between
Belize City (BZE) and San Pedro Sula. Fare is in the US$150+ range.
WEEKLY SHUTTLE BELIZE CITY—SAN PEDRO SULA
Another, fairly recent option is a weekly shuttle van/bus between
Belize City and San Pedro Sula. It leaves Belize City at 6 a.m.
Saturday from the Marine Terminal and is supposed to get to San Pedro
Sula at 6 p.m. that same day. Cost is US$60 one-way. I believe it
returns to Belize on Monday morning. Check with Mundo Maya Travel for
tickets. Email mundomayatravels@yahoo.com or call 501-223-0457.
PUBLIC BUSES
The other option is to take regular public buses between Belize's
western border at Benque Viejo through Guatemala to Honduras. Coming
from Honduras, one route would be to make your way to Puerto Barrios
or Rio Dulce, Guatemala, and from there bus to Flores and then to
Belize. I believe Linea Dorada has a bus that takes about 3 hours
from Rio Dulce to Flores, and you can continue on (about 5 hours) to
Belize City. Another, somewhat longer option is La Cieba-San Pedro
Sula-Guatemala City-Flores-Belize City. I believe Hedman Alas has a
daily bus from San Pedro Sula in the early afternoon to Guatemala
City, about 4 hours. From Guatemala Autobuses del Norte and a couple
of other lines have daily including overnight service to Flores. From
Flores, take Linea Dorada to Belize City.
EXIT TAXES
Note that the above prices don't include exit taxes and fees. The exit
tax by boat from Belize is US$3.75, by land US$18.75 and by air up to
almost US$40 if flying out of the international airport. Guatemala
and Honduras also have exit taxes.
--Lan Sluder
Belize First Magazine & Belize Blog www.belizefirst.com -- 735,000+ visitors
Live Better in Belize www.livebetterinbelize.com
Fodor's Belize 2009 -- just published by Fodor's/Random House
San Pedro Cool -- the only ad-free visitor guide to Ambergris Caye --
new 200-page eBook edition AVAILABLE NOW AS FREE DOWNLOAD from
www.belizefirst.com and www.livebetterinbelize.com
Living Abroad in Belize -- published by Avalon
Adapter Kit: Belize
Belize's Best Hotels & Restaurants -- eBook, available from
www.belizefirst.com and www.livebetterinbelize.com
Belize First Guide to Mainland Belize -- sold out, new edition coming
Easy Belize eBook -- updated version available on escapeartist.com at
www.escapeartist.com/e_Books/Belize2/Live_In_Belize.html and at
www.belizefirst.com

I just did the same trip on a much tighter schedule....bit the bullet and flew on Taca ($225 one way from San Pedro to Belize City). Only had 3 days at Caye Caulker, but it was worth it and then some. IMO everything about Caulker above the water and below it is better Utila....just more expensive...worth every penny IMO.