The beach
Playa Jacó
Visit Costa Rica describes Playa Jacó as a bay about 4 km long with dark sand and strong currents — and some of the best places to surf in the country.
The hostel's own listings put the sand a short walk away (30–50 m, depending on the listing).
Sources: Visit Costa Rica (ICT) — Central Pacific · Hostelworld (EN, property text) · Hostelworld (ES, property text)