Swimming Conundrum......

[Hymie]

I can swim the distance from the shore to a close-by island in 45 minutes, but today with tidal assistance it took me only 20 minutes to swim to the island. Assuming the tidal flow remains constant, how long will it take me to swim back from the island to shore?

Originally posted in Quizzes& Puzzles; people might have missed this – or it’s harder than I thought.

[1581960]

On the face of it, it looks like forever as the tidal effect is greater than the swim speed!

[sunny-dave]

Say it's 1.80 miles - therefore the normal swim speed is 2.4 mph - and the assisted swim speed is 5.4 mph.

So the current is 3mph and you'll never get home ...

[1581960]

Snap

[Hymie]

Yup, I’m stuck on the island until the tide turns.

When I first came across such a question, I thought the answer was 70 minutes, making the round trip without tidal assistance the same.