I was shopping insurance for my 98 Campion 542 the other day. I got a quote from Maxxam and did not require a survey, pictures only. I thought I would check with my house insurer. They needed a survey. Checked around and it was 375 bucks for an 18 foot boat with brand new motors, new gas lines, new steering. I was a bit surprised. I skipped the survey and went with Maxxam. The quote was from the Marine Butler. He says he is quite busy .
Just to add, it is likely money well spent if shopping for a boat. In my case not so necessary.