there's 3 simple ways:
- Use 3d water texture
- On terrain generator, make the relief as a wave
- Import some DXF object constructed as a wave
or:
-go to beach and make a photo of the water

For Links to Tutorials on how to do almost anything in Bryce you can go here...
http://www.3dlinks.com/tutorials_bryce.cfm
or here
http://www.brycetech.com/tutorials.html
or here
http://www.cincinnatilasalle.net/Downloads/Bryce/tutorials/
or here
http://www.halcyon.com/alrives/brycetips/tipindex_main.html
or here
http://www.petersharpe.com/

or to see what Bryce can do in the hands of a Master for insperation...
http://members.attcanada.ca/~m.murphy/3d.thumbs.html
and last but by no means the least......
http://www.billmunnsgallery.com/

Have Fun

lots of info, grog