The 52 GSF vessels, most of them currently near Crete, are carrying crews including politicians and Swedish climate change campaigner Greta Thunberg.
They set sail after experts from the UN-backed Integrated Food Security Phase Classification (IPC) confirmed there was a famine in Gaza City and warned it could spread to central and southern Gaza within weeks.
Mr Findlater, who said he felt a moral duty to take time off work to join the flotilla, said Tuesday’s attack happened in international waters.
He said: “These explosions were designed to inflict as much damage as possible to the boats to reduce the number of boats sailing towards Gaza.
“If they had landed any closer to one of us, we could have been seriously hurt.
“We’re worried about what’s next but we won’t stop because we know it’s absolutely nothing in the face of what Israel has been doing to those in Gaza and across Palestine for so many years.”