Vehicles and AoE effects

[Nagog]

So I'm running a session in a few minutes, and despite having 3 weeks to come.up with a solution, I can't find anything on how spells interact with vehicles.
The situation: The players have a small boat they're taking out to a larger ship where a cult is performing a ritual to wake a Kraken. The cult leader, knowing they're following him, used Control Water to place a whirlpool between them. How should I manage the required Str saves being made by a small fishing vessel?

[Kane0]

Easy mode: the vehicle fails any dex save and takes the damage
Hard mode: each 5’ section of vehicle fails any dex save and takes the damage

Wdit: Str saves would probably be based on size or the person providing propulsion (the rower)

[Unoriginal]

So I'm running a session in a few minutes, and despite having 3 weeks to come.up with a solution, I can't find anything on how spells interact with vehicles.
The situation: The players have a small boat they're taking out to a larger ship where a cult is performing a ritual to wake a Kraken. The cult leader, knowing they're following him, used Control Water to place a whirlpool between them. How should I manage the required Str saves being made by a small fishing vessel?

The spell is quite clear: only creatures can attempt the STR check. Objects are mentioned before that part, but not during it.

That being said, if you want the stats for the different boats in case other rule interactions happen, the Ghosts of Saltmarsh book has the stats and the rules for ship battles. Also exist as an Unearthed Arcana, in their unpolished version.