A really good question from David - which Stephen in his answer has identified the criteria for draft when cruising.
A reference to boats cruising in waters where coral reefs are the norm and where there are enormous tidal ranges, gives an opportunity to look at these cruising boats which left Darwin - Northern Australia - 26th July bound for Indonesia, Malaysia and Thailand. see :-
See CL- URL
The average length was just over 43 ft.
Here is a representative collection of similar size Cruisers with their drafts
1. Beneteau 423 ----------- 4'9"
2. Sabre 425 ----------- 4'9"
3. 42 Sabre Sabre ----------- 4'9"
4. 42 Catalina C42 ----------- 4'10"
5. Hunter 426 ----------- 5'0"
6. Folkes 42 ----------- 5'3"
7. S & S 42 ----------- 5'5"
8. C&C Landfall ----------- 5'6"
9. Whitby C/C Ketch 42 ----------- 5'8"
10. Gitana Cruiser ---------- 5'8"
11. Young Sun ---------- 5'8"
12. Beneteau Oceanis ---------- 5'11"
13. Gib Sea 126 ---------- 6'1"
14. Kettenburg 42 ----------- 6'2"
15. Bruce Roberts 42 ----------- 6'6"
16. Sam Crocker Cutter Ketch ------------ 6'6"
Average say 5' 7 " (1.72 metres)
Marinas may also prove a challenge to those boats that have drafts that exceed 7ft - as often the marina's design means that they are prone to silting up. Some - you can only get into at high tide.