Hi folks,
Had my first ever session in Cervantes yesterday. Didn't go too well. When going at full speed over the dark patch as shown on the attached photo the fin hit an underwater rock and I had a pretty bad crash. There are quite a few more similar patches scattered around the bay, I used to think it was just some sea grass. Is it all rocks and should be avoided?

There's a few around the one you hit that shouldn't be sailed over, the dark patch directly east of it definitely shouldn't. The dark patches directly to the south, are generally down to where the tide is at. The dark patches further south again (closer to the latitude of the island) are safe to sail over.
a side note, watch out for occy pots closer to shore. They're generally easy to site heading towards shore in Hansen bay, travelling out again into the sunset, not so much.