I do believe you can there are a few swimming areas around the lake. at the far end of lake by the end of dam is a water sports boating company that has guided tours, kayaks and stand up paddle boards.

Sorry can’t help you. It wasn’t breezy when we visited, but in reality that single observation doesn’t mean much.

There is a spot to enter for swimming where there is a hit with blue kayaks on a slope, may be in the east side, not fair from the main road

Yes. I just fish from the shore of Lake Arenal on the south end by the dam. Catch and release. I hit it up early morning and late afternoon and tend to stay pretty busy letting fish go. There are also guys like Captain Ron (look him up) that will take you out on a boat and put you on fish.

i have no idea i suppose they do since may travelers have big bags :)

I'm pretty sure that there are paddleboard rentals on either end of the highway that goes across the top of the dam on the way into La Fortuna.

I'm not sure as where we entered the Lake was the boat pickup and drop off. If you contact My Costa Rica they could answer your question. Enjoy your journey.

Rule of thumb with the weather there is: Jan-April - dry. May - July - could rain every day for short period of time. We did some trekking around volcano therefore it could be hot and humid in the summer. Then Aug - Dec - it could be pouring rain. We've met a couple who visited CR last Dec for 2 weeks - it was a constant rain. So, depending what you like, I recommend Jan-June time frame.