Die ptolemy scum!!!

They will turn on you eventually and maybe breaking the land border will allow the ai to take a break on you so you can trade across the mediteranean with them? Although the towns are small and underdeveloped at first. Depends if you want to roleplay politics more and 'find' a valid casus-belli. Maybe their 5th cousin looked at your wife the wrong way during a state dinner and now they must pay with land?

maybe not....