Abstract: Apparatus (10) for generating waves in a swimming pool comprises a plurality of wave generating chambers (11) each communicating with the pool through a below-the-water passageway (15) and having a closed upper portion (13) extending above the quiescent water level of the pool, each said upper portion (13) having first passageway means (16) connected via first fluid flow control means (17) to a pneumatic wave-generating medium (18) and second passageway means (19) connected via second fluid flow control means (20) to an aqueous wave generating medium (21), and operating means (30) connected to said first and second fluid flow control means (17, 20), said operating means (30) being arranged, in one mode, to cause intermitent delivery of said pneumatic wave-generating medium (18) to one of said chambers (11) to create a first wave-forming effect while simultaneously blocking delivery of said aqueous wave-generating medium (18) to said one chamber (11) and, in another mode, to cause delivery of said aqueous wave