Last year was a bad year for kelp. We had a lot of kelp loss in San Diego and at Catalina. This year it should come back with somewhat colder water. You are correct in planning to dive with the wet suit on Catalina in July. It would actually be ok even further north, if you are not too cold- sensitive. A one day trip to Channel Islands out of Ventura is doable. There are a couple of boats - Peace and Truth as far as I recall were very good.