We stayed at Pelican Eyes and chartered thier sailboat out for the day. We were a group of four and had a great time. Food and drink were included and as I remember it was quite reasonable. Have fun.

Ometepe is an overnight stay from SJDS!

Fishing- http://www.nicaraguafishingtrips.com

Lots of good places to eat and drink in SJDS, my fave is El Colibri

We actually did a (long) day trip to Ometepe from San Juan del Sur on Christmas Day in 2008o. Of course we would have preferred to stay overnight (at least), but the day trip was really worthwhile since we weren't going to be able to do an overnight.

We hired a guide from Pelican Eyes, Carlos, who made the trip possible--not sure we could have done it on our own, given the timeframe, and we certainly would not have gotten as much out of the trip. Carlos was full of information on Ometepe and took us to many of the highlights. We really appreciated that he gave up his Christmas day on our behalf. He charged a total of $145 for the full day trip (there were 6 of us, and van transportation to and from SJDS was included), and we supplemented that with a $20 tip. We opted for the 'first class' tickets on the ferry, about $2.50 each way, and sat on the top, open-air deck. It was awesome to see the twin volcanoes of Ometepe get closer and closer. Everything about the day was just perfect. Ometepe reminded us just a little bit of Molokai in the Hawaiian Islands.

One day while we were staying in SJDS we drove about 12 km on a truly bumpy dirt road to Playa Majagual, where we enjoyed a gorgeous cliff-ringed beach, great surf, and beautiful sand. A cute little grass hut for drinks, too, where we drank our favorite Nicaraguan beer, Toña, and one of us got a sharp sting from an unseen insect. (By the way, despite our fears, we were not overwhelmed by mosquitoes anywhere, though we always put on enough DEET-containing mosquito repellent to keep an elephant away).

We also did a fantastic night-time trip with Berman Gomez, from Pelican Eyes (Carlos's brother) to El Flor Reserve to see the turtles hatching. A sight to remember! We saw hundreds of baby turtles making their way out of their sand holes upon hatching, journeying the hundred yards or so down to the ocean under the full-moon sky. The trip was informative and fascinating. I definitely recommend doing it with a guide like Berman. The road to the reserve was rough and scarey to drive at night, with a couple of stream crossings, so a local driver is essential. We paid $25 per person for this great trip.

Another day trip to consider is to Granada--lots of great stuff to do there.

Here's a link to my trip report, if you're interested. http://www.fodors.com/community/mexico-central-america/2-weeks-in-nicaragua----color-calor-culture.cfm