Yokahu Kayaks (Carr. 987, km 6.2, Las Croabas, Fajardo, 787/863-5374 or 787/604-7375, yokahukayaks [at] hotmail [dot] com) offers kayak tours to Laguna Grande in Las Cabezas de San Juan  with licensed guides and equipment included. Reservations are required.
Kayaking Puerto Rico (787/435-1665 or 787/564-5629, info [at] kayakingpuertorico [dot] com, www.kayakingpuertorico.com ) offers bioluminescent plankton tours in Laguna Grande, as well as combination kayaking and snorkeling expeditions.
Las Tortugas Adventures (4 Calle La Puntilla, San Juan, 787/725-5169, info [at] kayak-pr [dot] com, www.kayak-pr.com ) offers kayak tours from Bahía Las Croabas to Las Cabezas de San Juan in Fajardo  and the mangrove forest in Piñones . No experience is necessary, and all equipment is provided. Reservations are required.