But not necessary the one with highest SPF. First, we should understand what SPF is.
If you get sun burn, without any protection, in 10 minutes, using an SPF 15 lotion will make you last 150 minutes. Simply put, SPF multiplies the amount of time exposed to sun. If you plan to stay under the sun for 4 hours (240 minutes), there isn’t much point using anything higher than SPF 24.
Why would you use SPF 100 products then? Either you will get burnt in 3 minutes without any protection, or you plan to stay under the full strength sun (noon time) for 17 hours.
It is a much better approach to use cheaper sun block products, and re-apply them periodically. People tend to use less higher SPF products, since they are more expensive. Remember, you are supposed to use about an ounce if you are wearing only swimming trunks or bikini. This means the 3-ouncet tube should last only several times.
Bottom line? Stick with SPF 30, apply them generously.
Several references:
New York Times, Life Hacker, WikiPedia.