We went on it twice this past weekend (Friday and Saturday). So my theory is that it depends on how heavy your boat is and where you sit! My 2 DDs, ages 9 and 12, and I--about 300 pounds total--were on the boat plus we had 2 strangers each time. Thus, our boat was lighter than when you have 5 adults.
The one time we had heavier strangers behind us (the man sat in the last seat and was probably above 250 pounds plus his wife might have been above 200), we definitely noticed we got far wetter. My youngest DD (who sat in the front both times) had her shirt drenched (as in practically see-through!) with the heavier couple behind us. But the first time we rode, it was with a young slim couple (probably under 275 pounds between the two of them), it was more of a spray and my older DD and I dried off before we even got back to GCH.