Fishing on Lake Arenal
Fish on a proper bass boat with live wells etc. It is the most pricey option but the most likely to succeed, (although there are never any guarantees with fishing!) For a half day (5 hours) it is $275 for the first 2 people and an additional $50 per extra person and for a full day (7.5 hours) it is $395 for the first 2 people and an additional $70 per extra person. It includes juice and beer, plus all the bait and tackle.
There is also the option of renting a boat and taking your own gear. You could also rent kayaks, pack a picnic and some gear and paddle out to the islands and fish off of them. Get in touch for a quote.