划 = row 骑 = ride rowing 划船 riding 骑车

骑马 划船 规划 划伤 划算

Actually, 划 refers to the movement of rowing. It's a verb. 划船means row/paddle a boat.(船=boat) 騎 is the verb "ride". It could be applied to a horse, a motorcycle and of course, a bicycle. So you see, it depends on the means of the transportation for the choice of your verb.

Bear234!,how are you? Just want to say thank you for your very helpful and clear reply. 谢谢您 have a lovely day!~~~:)

骑 comes from 骑马 u see the left part of 骑 is a 马(horse) so we use the verb 骑 when we want to describe the action like "riding a horse" such as bicyle, horse, moto etc in fact, you can use 骑 in chinese when it is “ride” in english. 划：when you make your arm or your hand or something held in your hand move in line or in circle, for example when you swim, or when you use a pen to draw a line, or when you paddle, you can use 划 for example, 划一条线在这张地图上 draw a line on this map. when you swim, your arms are moving to make your forward, what your arms do is called :划水 ofc when you paddle a boat, you 划水 too 划水 to make the boat move. but sometimes the chinese is just like this,..... too weird. we use 划船 to describe this situation: "sitting in a boat and paddle", even all know that we 划水 I hope you can understand this......