I play for a club where our home ground is quite close to the beach and the senior players talk about the influence the tide has on the pitch. Is it true?

No. It often has more to do with the afternoon sea breeze and rise in humidity.

Tide doesn’t generally influence ground water. Water travels through clay at around 3mm/hr which means for the water to move naturally in the soil profile enough to influence the clay based wicket it would have no effect. Often the sea breeze will bring in moisture that will assist swing bowlers. (Wacca)

Most often it is a superstition that batsmen use to mask their lack of result in an innings or twenty.

It’s funny but it is quite commonly said. I played for and Captained the Gosford CC and our home ground was Grahame Park in Gosford which sat next to and overlooking the picturesque Brisbane Water andplenty would say the decision on the toss was whether the tide was in or not. Can’t say I went with that though