Sailors didn't call our 'All's well' That was done by the street watchmen in towns and cities.
Ships' bells were chimed according to the the six four hour watches in a day, the Middle Watch (Midnight - 4am) Morning Watch (4am-8am) Forenoon Watch (8am-12 noon) Afternoon Watch ( 12 noon-4pm) Dog Watches ( 4-6, 6-8pm) the First Watch, (8pm-Midnight).
1-bell indicated the first half hour of the watch, ie 12.30am, 2 bells = 1am, 3 bells = 1.30am and so on to eight bells signifying the end of the Watch.
Calculations were done at sea by the sun and then by timepieces of one sort or another.