Step 1: Recall what salinity means.
Salinity is the amount of dissolved salt in water. More dissolved salt means higher salinity.
Step 2: Separate the two kinds of water.
Inland waters are rivers, lakes and ponds, which are fresh. Seas and oceans are the salty water bodies.
Step 3: Note the ocean value.
Sea water is quite salty, about 3.5 percent, that is 35 parts per thousand.
Step 4: Compare with inland water.
Fresh inland water holds far less salt than the sea, only a tiny fraction of that amount.
Step 5: Match with the options.
Values like 10 to 30 percent are far too high for fresh water, so they are wrong. The correct choice is less than 5 percent.
Step 6: Conclusion.
The saline concentration of inland waters is less than 5 percent.
\[ \boxed{\text{Less than 5\%}} \]