In a straight longbow riser, which is pretty small, the difference is noticeable, but not very much. The following is a specific gravity list of some favorite riser woods.
Kingwood 1.20, cocobolo 1.10, gaboon ebony 1.03, bloodwood .96, bubinga .88, wenge .88, granadillo .79, osage .76, zebra .74, hard maple .72, walnut .64.
Anything higher than 1.00 will sink in water.