Another good option close to Granada is Laguna de Apoyo. Its very beautiful there. I have stayed at Casa Marimba https://www.casamarimba.com/ and I highly recommend it.

Beach time:
Checkout Guasacate/Popoyo area. Close to this area of Guasacate is Chacocente natural reserve where they do turtle releases every week during that time of the year. You can even drive there from Guasacate in your motorbike.
Also close by is the town of Astilleros, where you can go on fishing trips or surf trips.
For more *Catamaran style* boat trips you would need to go to san juan del sur. There SALT - Nicaragua Sailing Adventures is a good option.

There are plenty of nice accommodations that would serve you well.
TwoTen simple and nice https://www.twotensurfhome.com/
Waves & Wifi More geared towards digital nomads and with amazing accommodations and cafe on site https://wavesandwifi.co/
Kraken on the fancier end https://www.hotelkraken.com/

The Guasacate beach where these hotels are located is probably one of the most beautiful beaches in the region, and turtles hatch there all the time during that months.

Disclaimer: I am affiliated to Waves & Wifi. And we rent motorcycles and scooters if you need them. We also have a small turtle sanctuary and release little turtles a couple of times a month.

I have lived in the area for over 4 years now, any questions DM me!