The Nigerian forward, who won his first caps for the Super Eagles in 2015, arrived at Vicarage Road from sister club Granada, originally agreeing a loan deal. The move was made permanent a few months later, and after a slow start in the Championship, the 25-year-old hit a great run of form.
35 games brought a return of 20 goals, including a run of 14 goals in 10 consecutive appearances. He netted vital strikes against Derby and Middlesbrough, and even though his form cooled off towards the end of the campaign, Ighalo still provided an all-round creative presence.
Swansea are looking to provide attacking cover for Bafetimbi Gomis, who has been leading the offensive line by himself since the departure of Wilfried Bony in January. Ighalo has proven himself in the Championship, but an £8 million fee seems excessive for a player with only one good season of goalscoring behind him, and who has yet to play in the Premier League.
If the Swans do submit a formal bid of that amount, it would come as a surprise if Watford were not to accept a deal, with there being no guarantees that Ighalo will be able to make the step up to the Premier League.