Exploring coastal caves safely?

Question

Having read this good question I felt it covered mountainous regions very well however myself and my husband are big fans of the coast and he certainly has (with his ex-fisherman father) explored many coastal caves over the years.

• What dangers or points to be aware of (tide, potential debris, etc) are there when exploring coastal caves?
• How would you safely explore a coastal cave? (would it be better over a few days etc...)

Answer 1

While this answer on a different question related to safety precautions for caving explains most of the what-to-have-along things, I'd like to put forth some points that can help you understand situation better.

1. Get confirmed information about Tide times and tide chart.
2. Avoid planning one such venture on a Full Moon or New Moon, since the Moon and the Sun both have their own impacts on sea tides. The general term for the tides during this span is called Spring Tides. The term 'Spring' is in accordance to the fact that water is higher than normal.
   The ideal time to plan one such venture is around Half Moon, during Neap Tides, since the Sun and the Moon are 90^o apart. This cancels the effect of both gravitational pulls. So there is no much difference in water levels at Low tide and High tide. This should allow you with added time to explore the cave. See if the tide chart also provides information about Apogee (The Moon's farthest location from the Earth in Earth's orbit) and Perigee (The Moon's closest location from the Earth in Earth's orbit). If you are not so much in love with tides at all then you can plan the venture around Apogee, the Moon will be farthest from the Earth and so the effect on tides will be minimum.
3. When you are in a coastal cave, a wave is the most dangerous thing to deal with. Unlike the case of normal mountain caves, in a coastal cave, you have to keep an eye on waves. When it hits you, you might get pushed towards walls which might injure you severely, you might bump onto one of your teammates, might get pushed into a narrow crack. The Key to safety here is being together and reachable, (which is not that critically needed in case of a mountain cave). The link to the other answer should help you with the kind of safety equipment you need to have along.
4. Its not just the waves you need to keep an eye on, you need to keep an eye on substantial increase in water levels. When entering deeper section of a cave, take necessary precautions in order to be prepared that if you are not out within the expected time and a wave hits you, it might lift you above the exit point to that deeper packet. In such a case, first see to it that you don't get hurt, and as the wave lapses, you'll have a very short time window to sneak out of the packet and turn elsewhere so that next wave doesn't send you back in. It is believed that rolling upside-down when the wave hits helps you hold your position better than being pushed.
5. While moving in or out of the cave, or anywhere around the cave, watch out for those sharp and slippery edges.

Lastly, someone should know when you are going in and by what time you plan to come out of it. If anything goes wrong, the person should be able to manage/initiate the rescue operation.

Answer 2

In addition to WedsPashi's answers, in the past when I've waded and scrambled around coasts I've gotten scratched and pierced by sharp mussels and rocks. I had a friend once step on a particularly long barnacle which broke inside his foot and we had to go to the ER. Also bear in mind that sea caves are formed in places that ocean currents batter the coast, and with those currents come nasty debris like glass. So in general, going barefooted or barehanded is not advisable.

Also, while WedaPashi is right about being wary of king tides, sometimes caves and beaches are only accessible at king low tides. These sites tend to have the most wildlife, too, because of their remoteness. Just make sure to be very vigilant to do all your exploring within +- 30 minutes of lowest tide so you don't get stranded.

Make sure you have a plan in case you do get stranded. For instance, one cave I explored like this had a strong current running parallel to the coast. If I ever got stranded, the plan was to stay afloat and ride the current to a beach down the way.