Is there any way to reuse a boat?

If you build a dock out of soul sand from The Nether, you should be able to manage even high-velocity docking procedure. Boats, like minecarts, don't disappear when you wander away, so as long as you don't accidentally deconstruct your boat, it should be waiting for you when you return.

In this way you can "dock" your boat simply by getting out of it by the soulsand.

I usually build a dock similar to this to aid in embarking and disembarking without my boat skipping away to the horizon.

To embark: hop in the boat, open the doors, and sail away. When you return, sail in, close the doors behind you, and hop out. It takes some practice to get out of without landing in the water, but I've never lost a boat with this setup.

I don't believe there is any way to pick up an assembled boat.

• You can break it, which will give you 3 wood and 2 sticks. If you carry a craft bench with you, this is 3/5 of a boat...
• A boat will only break apart if it runs into land at high speed. If you don't have any splash/wake coming off the sides, you're moving at a safe speed. You can then "use" the boat again to disembark (although it's worth noting that jumping off a boat in >1 block deep water can cause it to skid away at high speed and break - I manage to do this often)