At low tide, are there any land bridges from Vancouver Island to the mainland?

Nope, it is a ferry route.

If it was shallow enough for a bridge it would've been tried by now giving the ferry route is part of the highway.

https://youtu.be/H3NlWOY-eaU

Ahhhh..... just give her a swim.

No, not even close.  The straight is many kilometres wide, even at it's narrowest part.

NO land bridges.

They cross in bath tubs at certain times of the year,

Shallow depends on you definition.

Yeah, no.

It's way too deep and way too far.  

Uh...no. The water between Vancouver Island and the mainland is as deep as 1467 feet in places, and it averages 512 feet deep. If it was shallow enough to dry at low tide, it would be too shallow to run ferries across at most times of the day. And in most places, you wouldn't have time to walk across before the tide came in again even if the bottom was smooth enough to keep a normal walking speed, which it is not.

im from uk ..but have been to vancouver ..and the island ...no chance ..way too far and a busy shipping channel