yes the water line is painted around lap edges.
I launched my boat last weekend and the oil from my outboard , (which would not stay running) left a perfect waterline around hull, that is one way. A lot of people wait until boat is in water then mark it.
Dan Stober
1965 20' Cruisers Inc. 570 Seacamper
1962 20' Cruisers Inc. 502
1963 16' Cruisers Inc. 202 Seafarer
Weatherford, Texas