I’d stick with Amazon if I were you. All of my Amazon sites only have Amazon affiliate links. If you use Google Adsense display ads on your site, you’re literally taking people away from your site for the sake of just a few cents with these type of ads. If you direct them just to Amazon, then you have a greater chance of earning more money from that click.
As an affiliate for Boatbookings, you will receive 20% of their revenue - effectively meaning your commission will be about 4% of any sales from your referrals. You also receive 10% of any commissions Boatbookings make on repeat customers who were your referrals. They do have a minimum charter value of 3,000 ($/€/£/etc) before commissions are earned.