Jim Manly, who is also an ordained United Church minister, was travelling with several European legislators and pro-Palestinian activists when he was taken into Israeli custody over the weekend.
The 79-year-old was on the Finnish-flagged MV Estelle to draw attention to what he called the struggles of the Palestinians living in the Gaza Strip.
His family says they want Ottawa to do more to help have Manly released.
His son, Paul Manly, says his father should be permitted to call his family and should not be forced to sign any type of confession.
The vessel was reportedly carrying aide supplies when it was intercepted and diverted to an Israeli port.
"My father must be released from detention immediately and put on the first plane available back to Canada," he said.
An official for Foreign Affairs Minister John Baird said Monday the government recognizes Israel's "legitimate security concerns" over flotillas into Gaza.
"We have strongly urged those wishing to deliver humanitarian goods to the Gaza Strip to do so through established channels. Unauthorized efforts to deliver aid are provocative and, ultimately, unhelpful to the people of Gaza," Baird's spokesman, Rick Roth, said in an email.
The ministry says it is monitoring the situation closely and has been in contact with Manly's family.
Israel's Interior Ministry says the activists will be questioned and deported to their home countries within 72 hours.
Israel imposed an embargo on Gaza after the Islamic militant organization seized control of the territory in 2007.
Israel says it needs the blockade to prevent smuggling of weapons.
But critics say the embargo amounts to the collective punishment of Gaza's residents.
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