There's something to be said for shore diving. No boats to wait for, no people to annoy you---you dive when and where you want. Even places you wouldn't expect (like New York and New Jersey) can have decent shore diving.
If you spend any time reading about shore diving, either from books or the internet, you're bound to come across the term slack tide, or sometimes, slack water. Slack tide refers to the time between high and low tides, when the tide is changing. That means there are four a day in most places.
During this time the water is relatively calm, because you don't have excess water rushing away (low tide) or toward (high tide) the coast. This makes it particularly significant to shore divers. In many places, slack tide is the only safe time to scuba dive. Diving any other time and either you can't enter the water (high tide) or the water will quickly carry you to sea (low tide).
When shore diving a new spot, read up or talk to people and find out if a slack tide entry is considered a must. If it's not a must, it often turns what would otherwise be an advanced dive with strong current into an easy dive that could even be used for beginner's certification.
A downside to slack tide is visibility. Calm water means there's nothing to move particle matter in the water and visibility tends to go down. If you have the option, weigh that into your next shore dive scheduling.
Many websites and weather reporting services give the times of the daily tides. They are very predictable and can be calculated far in advance. Search for your location and terms like "tide tables" to find them.