figure 1

make a plain blue background
create a new layer, and airbrush some relatively wide lines to simulate water waves
set the opacity to 50%
use Filter>Distort>Ripple, or Ocean Ripple, to distort the layer
rotate the layer using Free Transform
repeat with a new layer, but this time play with curves to get the narrow lines, similar to what you would see on the actual pool bottom.
Drag this second layer underneath the waves, as it would be in reality.
If you want, download the actual psd file that was used to make figure 1.

[an error occurred while processing this directive] <% fp_sQry="SELECT * FROM Results" fp_sDefault="" fp_sNoRecords="No records returned." fp_sDataConn="PoolBottom" fp_iMaxRecords=256 fp_iCommandType=1 fp_iPageSize=0 fp_fTableFormat=False fp_fMenuFormat=False fp_sMenuChoice="" fp_sMenuValue="" fp_iDisplayCols=3 fp_fCustomQuery=False BOTID=0 fp_iRegion=BOTID %> [an error occurred while processing this directive]

<%=FP_FieldVal(fp_rs,"User_name")%>, <%=FP_FieldVal(fp_rs,"Timestamp")%>, <%=FP_FieldVal(fp_rs,"PoolBottom")%>

[an error occurred while processing this directive]

Here's a way to make a rippled water pattern, such as you would see on the bottom of a pool.