From my experience, it only drains when the serpent is moving in away from you.

So what I do is hook it, then I try to keep pace with it as we approach shore. If it starts swimming away, I'll drop to paddle, or even reverse speeds. Until it locks back on to me and then I'll speed up again.

It's definitely more tricky to rope it now, but with practice you can still totally do it solo.

And, as mentioned above, you can always just half-sail into shallows and fight it there. Most of them will still try to attack you there.