The ferry costs about $15 each way and takes 40 minutes.

The bus station is just up the hill from the ferry dock. Collectivos are two more blocks from there.

Yes, it's safe.

LBI is correct. That will be a tough way to go in one day. You might want to charter a boat from Coz directly to Tulum Ruins. 8 people might make it an effective price point and much more enjoyable.

That is one of the big reasons the Port of Calica is receiving more cruise traffic and the impetus for rumors about a high speed train.