Marina Marlin Cienfuegos (Calle 35, e/ 6 y 8, tel. 043/55-1699, operativo [at] nautica [dot] cfg [dot] tur [dot] cu) offers scuba diving (CUC30 one dive) from Hotel Rancho Luna. Marina Marlin also offers two-hour bay excursions aboard the Flipper catamaran (9 a.m., 11 a.m., 2 p.m., and 5 p.m., CUC10 per person).
Germany-based Plattensail (www.platten-sailing.de [1]) offers long-term yacht charters at the marina, and you can rent catamarans (one-day to one-month rentals) with Bluesail (tel. 043/55-6119, www.bluesail-caribe.com [2]) at Club Cienfuegos (Calle 37, e/ Av. 8 y 12, Sun.–Fri. 10 p.m.–2 a.m., Sat. until 2 a.m.). The club grounds also have crazy cars (carros locos, CUC1), go-karts, and tennis.
The Hotel Unión has a gym, aerobics, swimming pool, and sauna, all open to the public.
Estadio 5 de Septiembre (Av. 20, e/ 45 y 55, tel. 043/51-3644) hosts baseball games October–May.
Links:
[1] http://www.platten-sailing.de
[2] http://www.bluesail-caribe.com