What are the 2 branches of seamanship?

Answer 1

There's actually 3 types, but most consider Deck and Marlinespike to be the primary 2.

Deck Seamanship - General seamanship that involves the work that goes on about the ship's deck, as well as the equipment used to perform that work. Such examples are Mooring, Anchoring, Rigging, and Handling.

Boat Seamanship - Anything involved with the handling of small boats.

Marlinespike Seamanship - Marlinespike seamanship concerns the use and care of mooring/rigging lines. It centers on the art of forming knots, making splices in rope and line, and fashioning useful and decorative articles from lines, twine, and similar material. Making a heaving line ("heavie)" is one example of the different aspects of Marlinespike seamanship used to create a very necessary and useful item.

Answer 2

Marlinespike (lines, ropes, knots, etc.) and Deck (equipment handling).