CREATE TABLE table_721 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

who are the candidates where the incumbent is sam m. gibbons?
SELECT "Candidates" FROM table_721 WHERE "Incumbent" = 'Sam M. Gibbons'
SELECT "Candidates" FROM "table_721" WHERE "Incumbent" = 'Sam M. Gibbons'